title: Peter Navarro

text: Navarro has been a staunch critic of trade with China and strong proponent of reducing U.S. trade deficits. He has attacked Germany, Japan and China for their currency manipulation. He has called for increasing the size of the American manufacturing sector, setting high tariffs, and repatriating global supply chains. He was a fierce opponent of the Trans-Pacific Partnership.


title: Peter Navarro

text: According to Bloomberg News, Navarro had "roots as a mainstream economist" as he voiced support for free trade in his 1984 book "The Policy Game". He changed his positions as he saw "the globalist erosion of the American economy" develop. He would later become a critic of the North American Free Trade Agreement (NAFTA).


title: Peter Navarro

text: According to "Politico", Navarro's economic theories are "considered fringe" by his fellow economists. A "New Yorker" reporter described Navarro's views on trade and China as so radical "that, even with his assistance, I was unable to find another economist who fully agrees with them."


title: Peter Navarro

text: "The Economist" described Navarro as having "oddball views". The George Mason University economist Tyler Cowen has described Navarro as "one of the most versatile and productive American economists of the last few decades", but Cowen noted that he disagreed with his views on trade, which he claimed go "against a strong professional consensus." University of Michigan economist Justin Wolfers described Navarro's views as "far outside the mainstream," noting that "he endorses few of the key tenets of" the economics profession. According to Lee Branstetter, economics professor at Carnegie Mellon University and trade expert with the Peterson Institute for International Economics, Navarro "was never a part of the group of economists who ever studied the global free-trade system ... He doesn't publish in journals. What he's writing and saying right now has nothing to do with what he got his Harvard Ph.D. in ... he doesn't do research that would meet the scientific standards of that community." Marcus Noland, an economist at the Peterson Institute for International Economics, described a tax and trade paper written by Navarro and Wilbur Ross for Trump as "a complete misunderstanding of international trade, on their part."


title: Peter Navarro

text: In August 2019, Navarro asserted the tariffs of the ongoing China–United States trade war were not hurting Americans. Citing extensive evidence to the contrary, Politifact rated Navarro's assertion "Pants on Fire."


title: Peter Navarro

text: Navarro supports a tax policy called "border adjustment", which, as commonly used in the VATs of most countries, taxes all imports at the domestic rate while rebating tax on exports, essentially transforming taxes from taxes on production to taxes on consumption. In response to criticism that the border adjustment tax could hurt U.S. companies and put jobs at risk, Navarro called it "fake news".


title: Peter Navarro

text: According to "Politico", "Navarro is perhaps the most extreme advocate in Washington, and maybe in all of economics, for an aggressive stance toward China." Navarro put his attention to China in the mid-2000s. His first publication on the subject is the 2006 book "". Navarro has said that he started to examine China when he noticed that his former students were losing jobs, concluding that China was at fault.


title: Peter Navarro

text: In "Politico"s description of the book, "Navarro uses military language to refer to China's trade policies, referring to its 'conquest' of the world's export markets, which has 'vaporized literally millions of manufacturing jobs and driven down wages.' ... China's aspirations are so insatiable, he claims, that eventually there will be a clash over "our most basic of all needs—bread, water, and air.'" Navarro has described the entry of China to the World Trade Organization as one of the United States' biggest mistakes. To respond to the threat posed to the United States, Navarro has advocated for 43% tariffs, the repudiation of trade pacts, major increases in military expenditures and strengthened military ties with Taiwan. "The New York Times" notes that "a wide range of economists have warned that curtailing trade with China would damage the American economy, forcing consumers to pay higher prices for goods and services." Navarro has reportedly also encouraged Trump to enact a 25% tariff on Chinese steel imports, something that "trade experts worry... would upend global trade practices and cause countries to retaliate, potentially leading to a trade war".


title: Peter Navarro

text: Navarro has said that a large part of China's competitive advantage over the United States stems from unfair trade practices. Navarro has criticized China for pollution, poor labor standards, government subsidies, producing "contaminated, defective and cancerous" exports, currency manipulation, and theft of US intellectual property. In his 2012 documentary, Navarro said that China caused the loss of 57,000 US factories and 25 million jobs. Navarro has maintained that China manipulates its currency and, on August 5, 2019, the U.S. Treasury Department officially designated China as a "currency manipulator."


title: Peter Navarro

text: Of the more than dozen China specialists contacted by "Foreign Policy", most either did not know of Navarro or had only interacted with him briefly. Kenneth Pomeranz, University of Chicago professor of Chinese History, said that his "recollection is that [Navarro] generally avoided people who actually knew something about the country." Columnist Gordon G. Chang was the only China watcher contacted by "Foreign Policy" who defended Navarro, but even he noted that he disagreed with Navarro's claims of currency manipulation, opposition to the TPP, and calls for high tariffs. James McGregor, a former chairman of the American Chamber of Commerce in China, said that Navarro's books and documentary on China "have close to zero credibility with people who know the country," and are filled with "hyperbole, inaccuracies" and a "cartoonish caricature of China that he puts out."


title: Peter Navarro

text: Some of Navarro's views on China fit within the mainstream, such as criticism of Chinese currency manipulation (pre-2015), concern that China's rapid ascension to the World Trade Organization harmed the Rust Belt, and criticism of China's weak environmental regulations and poor labor standards.


title: Peter Navarro

text: In six of his books about China, Navarro quotes a "Ron Vara", whom he describes as a China hawk and former Harvard PhD doctoral student in economics, and who says Sinophobic things about China and the Chinese. An investigation by the "Chronicle of Higher Education" found that no such person existed, and that Ron Vara (an anagram of Navarro) appeared to represent views that Navarro himself held. Navarro has admitted to making up the character, an author surrogate, and quoting him in his books. Economist Glenn Hubbard, who co-authored "Seeds of Destruction" with Navarro, has said he was not aware that Vara was fictional, and that he did not approve of Navarro attributing information to a fictional source. In December 2019, a memo apparently authored by Ron Vara began circulating in Washington DC. The memo highlighted the "Keep Tariff Argument" and the use of tariffs against China a few days before an additional 15% tariff on $160 billion of Chinese made goods was set to be implemented. Navarro later confirmed that he had written the memo.


title: Peter Navarro

text: In response to the "Ron Vara" character, Ministry of Foreign Affairs of the People's Republic of China spokesperson Hua Chunying accused Navarro of "smearing China with lies".。


title: Peter Navarro

text: Navarro drew controversy when he accused Germany of using a "grossly undervalued" euro to "exploit" the US and the rest of the European Union. "Politico" noted that the German government does not set the value of the euro. Economists and commentators are divided on the accuracy of Navarro's remarks. Economist Paul Krugman said that Navarro was right and wrong at the same time: "Yes, Germany in effect has an undervalued currency relative to what it would have without the euro... But does this mean that the euro as a whole is undervalued against the dollar? Probably not." Boston University economist Laurence Kotlikoff described Navarro's accusation of Germany as a currency manipulator as "#stupideconomics".


title: Peter Navarro

text: Navarro argues that the decline in US manufacturing jobs is chiefly due to "unfair trade practices and bad trade deals. And if you don't believe that, just go to the booming factories in Germany, in Japan, in Korea, in China, in Malaysia, in Vietnam, in Indonesia, in Italy—every place that we're running deficits with." However, many economists attribute the decline in manufacturing jobs chiefly to automation and other innovations that allow manufacturing firms to produce more goods with fewer workers, rather than trade.


title: Peter Navarro

text: Navarro has been a proponent of strengthening the manufacturing sector's role in the national economy: "We envision a more Germany-style economy, where 20 percent of our workforce is in manufacturing. ... And we're not talking about banging tin in the back room." "The New York Times" notes that "experts on manufacturing ... doubt that the government can significantly increase factory employment, noting that mechanization is the major reason fewer people are working in factories."


title: Peter Navarro

text: Navarro has called for the United States to leave the North American Free Trade Agreement, and has tried to convince Trump to initiate a withdrawal.


title: Peter Navarro

text: Navarro has called for repatriating global supply chains. According to "Politico"'s Jacob Heilbrunn, such a move "would be enormously costly and take years to execute".


title: Peter Navarro

text: Navarro has characterized foreign purchases of U.S. companies as a threat to national security, but according to NPR, this is "a fringe view that puts him at odds with the vast majority of economists." Dartmouth economist Douglas Irwin noted that the US government already reviews foreign purchases of companies with military or strategic value, and has on occasion rejected such deals. Irwin said that Navarro had not substantiated his claim with any evidence.


title: Peter Navarro

text: Navarro has also said that the United States has "already begun to lose control of [its] food supply chain", which according to NPR, "sounded pretty off-the-wall to a number of economists" who noted that the US is a massive exporter of food. Dermot Hayes, an agribusiness economist at Iowa State University, described Navarro's statement as "uninformed".


title: Peter Navarro

text: Navarro criticized the outsourcing of critical materials — like the production of essential medical supplies — to China.


title: Peter Navarro

text: Navarro is a proponent of the notion that trade deficits are bad in and of themselves, a view which is widely rejected by trade experts and economists. In a white paper co-authored with Wilbur Ross, Navarro stated, "when a country runs a trade deficit by importing more than it exports, this subtracts from growth." In a "Wall Street Journal" op-ed defending his views, Navarro stated, "If we are able to reduce our trade deficits through tough, smart negotiations, we should be able to increase our growth." Harvard University economics professor Gregory Mankiw has said that Navarro's views on the trade deficit are based on the kind of mistakes that "even a freshman at the end of ec 10 knows." Tufts University professor Daniel W. Drezner said about Navarro's op-ed, "as someone who's written on this topic I could not for the life of me understand his reasoning". According to Tyler Cowen, "close to no one" in the economics profession agrees with Navarro's idea that a trade deficit is bad in and of itself. Nobel laureate Angus Deaton described Navarro's attitude on trade deficits as "an old-fashioned mercantilist position."


title: Peter Navarro

text: "The Economist" has described Navarro's views on the trade deficit as "dodgy economics", while the "Financial Times" has described them as "poor economics". Economists Noah Smith, Scott Sumner, Olivier Blanchard, and Phil Levy have also criticized Navarro's views on the trade deficit. Dan Ikenson, director of the Cato Institute's Herbert A. Stiefel Center for Trade Policy Studies, goes so far as to call Navarro a "charlatan" and says that "99.9 per cent of respectable economists would eschew" what he says: "He says imports deduct from output, and he calls that accounting identity the 'economic growth formula'. He thinks that for every dollar we import, our GDP is reduced by a dollar. I don't know how he got his PhD at Harvard."


title: Peter Navarro

text: Navarro opposes the Trans-Pacific Partnership. In an April 2015 op-ed, Navarro said, "To woo us, their spinmeisters boast the TPP will spur American exports to stimulate sorely needed economic growth. In truth, the American economy will suffer severely. This is because the TPP will hammer two main drivers of economic growth—domestic investment and 'net exports.'" Navarro said in March 2017 that TPP "would have been a "death knell" to America's auto and vehicle parts industry that we "urgently need to bring back to full life." "Politico"'s Jacob Heilbrunn and "the" "Economist" argue that there may be a disconnect between Navarro's policy on China and his opposition to the TPP, as scuttling the TPP will strengthen China's hand.


title: Peter Navarro

text: In 2001 Navarro married Leslie Lebon, a California architect. The couple lived in Laguna Beach with Lebon's son from a previous marriage while Navarro was a professor at UC Irvine. In late 2018, Lebon filed for divorce in Orange County. Their divorce became final in December 2020.


title: University College, Oxford

text: University College (in full The College of the Great Hall of the University of Oxford, colloquially referred to as "Univ") is a constituent college of the University of Oxford in England. It has a claim to being the oldest college of the university, having been founded in 1249 by William of Durham.


title: University College, Oxford

text: The college is associated with a number of influential people, including Clement Attlee, Harold Wilson, Bill Clinton, Neil Gorsuch, Stephen Hawking, C. S. Lewis, V. S. Naipaul, Robert Reich, William Beveridge, Bob Hawke, Robert Cecil, and Percy Bysshe Shelley.


title: University College, Oxford

text: A legend arose in the 14th century that the college was founded by King Alfred in 872. This explains why the college arms are those attributed to King Alfred, why the Visitor is always the reigning monarch, and why the college celebrated its millennium in 1872. Most agree that in reality the college was founded in 1249 by William of Durham. He bequeathed money to support ten or twelve masters of arts studying divinity, and a property which became known as Aula Universitatis (University Hall) was bought in 1253. This later date still allows the claim that Univ is the oldest of the Oxford colleges, although this is contested by Balliol College and Merton College. Univ was only open to fellows studying theology until the 16th century.


title: University College, Oxford

text: The college acquired four properties on its current site south of the High Street in 1332 and 1336 and built a quadrangle in the 15th century. As it grew in size and wealth, its medieval buildings were replaced with the current Main Quadrangle in the 17th century. Although the foundation stone was placed on 17 April 1634, the disruption of the English Civil War meant it was not completed until sometime in 1676. Radcliffe Quad followed more rapidly by 1719, and the library was built in 1861.


title: University College, Oxford

text: Like many of Oxford's colleges, University College accepted its first mixed-sex cohort in 1979, having previously been an institution for men only.


title: University College, Oxford

text: The main entrance to the college is on the High Street and its grounds are bounded by Merton Street and Magpie Lane. The college is divided by Logic Lane, which is owned by the college and runs through the centre. The western side of the college is occupied by the library, the hall, the chapel and the two quadrangles which house both student accommodation and college offices. The eastern side of the college is mainly devoted to student accommodation in rooms above the High Street shops, on Merton Street or in the separate Goodhart Building. This building is named after former master of the college, Arthur Lehman Goodhart.


title: University College, Oxford

text: A specially constructed building in the college, the Shelley Memorial, houses a statue by Edward Onslow Ford of the poet Percy Bysshe Shelley – a former member of the college, who was sent down for writing "The Necessity of Atheism" (1811), along with his friend T. J. Hogg. Shelley is depicted lying dead on the Italian seashore.


title: University College, Oxford

text: The college annexe on Staverton Road in North Oxford houses undergraduate students during their second year and some graduate students.


title: University College, Oxford

text: The college also owns the University College Boathouse (completed in 2007 and designed by Belsize architects) and a sports ground, which is located nearby on Abingdon Road.


title: University College, Oxford

text: The Alternative Prospectus is written and produced by current students for prospective applicants. The publication was awarded a HELOA Innovation and Best Practice Award in 2011. The Univ Alternative Prospectus offers student written advice and guidance to potential Oxford applicants. The award recognises the engagement of the college community, unique newspaper format, forward-thinking use of social media and the collaborative working between staff and students.


title: University College, Oxford

text: University has the longest grace of any Oxford (and perhaps Cambridge) college. It is read before every Formal Hall, which is held on Tuesdays, Thursdays, and Sundays. The reading is performed by a Scholar of the college and whoever is sitting at the head of High Table (typically the Master, or the most senior Fellow at the table if the Master is not dining).


title: University College, Oxford

text:
SCHOLAR – "Benedictus sit Deus in donis suis."
RESPONSE – "Et sanctus in omnibus operibus suis."
SCHOLAR – "Adiutorium nostrum in Nomine Domini."
RESPONSE – "Qui fecit coelum et terram."
SCHOLAR – "Sit Nomen Domini benedictum."
RESPONSE – "Ab hoc tempore usque in saecula."
SCHOLAR – "Domine Deus, Resurrectio et Vita credentium, Qui semper es laudandus tam in viventibus quam in defunctis, gratias Tibi agimus pro omnibus Fundatoribus caeterisque Benefactoribus nostris, quorum beneficiis hic ad pietatem et ad studia literarum alimur: Te rogantes ut nos, hisce Tuis donis ad Tuam gloriam recte utentes, una cum iis ad vitam immortalem perducamur. Per Jesum Christum Dominum nostrum."
RESPONSE - "Amen."
SCHOLAR — "Deus det vivis gratiam, defunctis requiem: Ecclesiae, Regi, Regnoque nostro, pacem et concordiam: et nobis peccatoribus vitam aeternam."
RESPONSE - "Amen."


title: University College, Oxford

text:
SCHOLAR — "Let God be blessed in his gifts."
RESPONSE — "And holy in all his works."
SCHOLAR — "Our help is in the Name of the Lord."
RESPONSE — "Who has made heaven and earth."
SCHOLAR — " May the Name of the Lord be blessed."
RESPONSE — "From this time for evermore."
SCHOLAR — "Lord God, the resurrection and the life of them that believe, who is always to be praised both among the living and among the dead, we give You thanks for all our founders and other benefactors, by whose gifts we are nourished here for piety and the study of learning; asking You that we, using these Your gifts rightly to Your glory, may be led together with them into eternal life. Through Jesus Christ our Lord."
RESPONSE — "Amen."
SCHOLAR — "May God grant to the living grace, and to the dead rest; to the Church, the King, and our realm, peace and concord; and to us sinners everlasting life."
RESPONSE — "Amen."


title: University College, Oxford

text: Many influential politicians are associated with the college, including the social reformer and author of the Beveridge Report William Beveridge (who was a master of University College) and two UK Prime Ministers: Clement Attlee and Harold Wilson (a Univ fellow). US President Bill Clinton (though he did not graduate) and Prime Minister of Australia, Bob Hawke were also students. Other heads of state and government to have attended Univ include Edgar Whitehead (Rhodesia), Kofi Abrefa Busia (Ghana), and Festus Mogae (Botswana). Nobel Peace Prize Laureate Robert Cecil studied law at the college, similarly U.S. Supreme Court Associate Justice Neil Gorsuch received a DPhil in law as a Marshall Scholar, while former NATO Supreme Allied Commander Bernard W. Rogers read Philosophy, Politics and Economics as a Rhodes Scholar, and former Court of Justice of the European Communities Judge Sir David Edward read Classics.


title: University College, Oxford

text: In the arts, people associated with the college include poet Percy Bysshe Shelley (expelled for writing "The Necessity of Atheism"), for whom there is a memorial in college; Poet Laureate Andrew Motion; author of the "Narnia" books C. S. Lewis; and a Nobel Prize for Literature winner, Sir V. S. Naipaul. One of the translators of the King James Bible, George Abbot, was a master of the college. The actors Michael York and Warren Mitchell attended Univ, as well as broadcaster Paul Gambaccini.


title: University College, Oxford

text: It was due to the college's lack of a mathematics fellow (this is no longer the case) that Stephen Hawking read a natural sciences degree and ended up specialising in physics. Other former students include John Radcliffe (physician), William Jones (philologist), and Edmund Cartwright (inventor). Rudolph A. Marcus, a Canadian-born chemist who received the 1992 Nobel Prize in Chemistry, received a Professorial Fellowship at Univ from 1975 to 1976. A perhaps more unusual alumnus is Prince Felix Yusupov, the assassin of Rasputin.


title: University College, Oxford

text: Univ had the highest proportion of old members offering financial support to the college of any Oxbridge college with 28% in 2007.


title: University College, Oxford

text: Although not members of University College, the scientists Robert Boyle (sometimes described as the "first modern chemist") and his assistant (Robert Hooke, architect, biologist, discoverer of cells) lived in Deep Hall (then owned by Christ Church and now the site of the Shelley Memorial). The former made a contribution to the completion of University College's current Hall in the mid-17th Century.


title: University College, Oxford

text: Samuel Johnson (author of "A Dictionary of the English Language" and a member of Pembroke College) was a frequent visitor to the Senior Common Room at University College during the 18th Century.


title: University College, Oxford

text: The "University College Record" is the annual magazine sent to alumni of the college each autumn. The magazine provides college news on clubs and societies such as the University College Players and the Devas Club, as well as academic performance and prizes. News about and obituaries of former students are included at the end of each issue.


title: Verification and validation

text: Verification and validation (also abbreviated as V&V) are independent procedures that are used together for checking that a product, service, or system meets requirements and specifications and that it fulfills its intended purpose. These are critical components of a quality management system such as ISO 9000. The words "verification" and "validation" are sometimes preceded with "independent", indicating that the verification and validation is to be performed by a disinterested third party. "Independent verification and validation" can be abbreviated as "IV&V".


title: Verification and validation

text: In practice, as quality management terms, the definitions of verification and validation can be inconsistent. Sometimes they are even used interchangeably.


title: Verification and validation

text: However, the PMBOK guide, a standard adopted by the Institute of Electrical and Electronics Engineers (IEEE), defines them as follows in its 4th edition:


title: Verification and validation

text: Verification is intended to check that a product, service, or system meets a set of design specifications. In the development phase, verification procedures involve performing special tests to model or simulate a portion, or the entirety, of a product, service, or system, then performing a review or analysis of the modeling results. In the post-development phase, verification procedures involve regularly repeating tests devised specifically to ensure that the product, service, or system continues to meet the initial design requirements, specifications, and regulations as time progresses. It is a process that is used to evaluate whether a product, service, or system complies with regulations, specifications, or conditions imposed at the start of a development phase. Verification can be in development, scale-up, or production. This is often an internal process.


title: Verification and validation

text: Validation is intended to ensure a product, service, or system (or portion thereof, or set thereof) results in a product, service, or system (or portion thereof, or set thereof) that meets the operational needs of the user. For a new development flow or verification flow, validation procedures may involve modeling either flow and using simulations to predict faults or gaps that might lead to invalid or incomplete verification or development of a product, service, or system (or portion thereof, or set thereof). A set of validation requirements (as defined by the user), specifications, and regulations may then be used as a basis for qualifying a development flow or verification flow for a product, service, or system (or portion thereof, or set thereof). Additional validation procedures also include those that are designed specifically to ensure that modifications made to an existing qualified development flow or verification flow will have the effect of producing a product, service, or system (or portion thereof, or set thereof) that meets the initial design requirements, specifications, and regulations; these validations help to keep the flow qualified. It is a process of establishing evidence that provides a high degree of assurance that a product, service, or system accomplishes its intended requirements. This often involves acceptance of fitness for purpose with end users and other product stakeholders. This is often an external process.


title: Verification and validation

text: It is sometimes said that validation can be expressed by the query "Are you building the right thing?" and verification by "Are you building it right?". "Building the right thing" refers back to the user's needs, while "building it right" checks that the specifications are correctly implemented by the system. In some contexts, it is required to have written requirements for both as well as formal procedures or protocols for determining compliance.


title: Verification and validation

text: It is entirely possible that a product passes when verified but fails when validated. This can happen when, say, a product is built as per the specifications but the specifications themselves fail to address the user's needs.


title: Verification and validation

text: Verification of machinery and equipment usually consists of design qualification (DQ), installation qualification (IQ), operational qualification (OQ), and performance qualification (PQ). DQ may be performed by a vendor or by the user, by confirming through review and testing that the equipment meets the written acquisition specification. If the relevant document or manuals of machinery/equipment are provided by vendors, the later 3Q needs to be thoroughly performed by the users who work in an industrial regulatory environment. Otherwise, the process of IQ, OQ and PQ is the task of validation. The typical example of such a case could be the loss or absence of vendor's documentation for legacy equipment or do-it-yourself (DIY) assemblies (e.g., cars, computers, etc.) and, therefore, users should endeavour to acquire DQ document beforehand. Each template of DQ, IQ, OQ and PQ usually can be found on the internet respectively, whereas the DIY qualifications of machinery/equipment can be assisted either by the vendor's training course materials and tutorials, or by the published guidance books, such as "step-by-step" series if the acquisition of machinery/equipment is not bundled with on- site qualification services. This kind of the DIY approach is also applicable to the qualifications of software, computer operating systems and a manufacturing process. The most important and critical task as the last step of the activity is to generating and archiving machinery/equipment qualification reports for auditing purposes, if regulatory compliances are mandatory.


title: Verification and validation

text: Qualification of machinery/equipment is venue dependent, in particular items that are shock sensitive and require balancing or calibration, and re-qualification needs to be conducted once the objects are relocated. The full scales of some equipment qualifications are even time dependent as consumables are used up (i.e. filters) or springs stretch out, requiring recalibration, and hence re-certification is necessary when a specified due time lapse. Re-qualification of machinery/equipment should also be conducted when replacement of parts, or coupling with another device, or installing a new application software and restructuring of the computer which affects especially the pre-settings, such as on BIOS, registry, disk drive partition table, dynamically-linked (shared) libraries, or an ini file etc., have been necessary. In such a situation, the specifications of the parts/devices/software and restructuring proposals should be appended to the qualification document whether the parts/devices/software are genuine or not. Torres and Hyman have discussed the suitability of non-genuine parts for clinical use and provided guidelines for equipment users to select appropriate substitutes which are capable of avoiding adverse effects. In the case when genuine parts/devices/software are demanded by some of regulatory requirements, then re-qualification does not need to be conducted on the non-genuine assemblies. Instead, the asset has to be recycled for non-regulatory purposes.


title: Verification and validation

text: When machinery/equipment qualification is conducted by a standard endorsed third party such as by an ISO standard accredited company for a particular division, the process is called certification. Currently, the coverage of ISO/IEC 15408 certification by an ISO/IEC 27001 accredited organization is limited; the scheme requires a fair amount of efforts to get popularized.


title: Verification and validation

text: These terms generally apply broadly across industries and institutions. In addition, they may have very specific meanings and requirements for specific products, regulations, and industries. Some examples:


title: Miss Havisham

text: Miss Havisham is a character in the Charles Dickens novel "Great Expectations" (1861). She is a wealthy spinster, once jilted at the altar, who insists on wearing her wedding dress for the rest of her life. She lives in a ruined mansion with her adopted daughter, Estella. Dickens describes her as looking like "the witch of the place".


title: Miss Havisham

text: Although she has often been portrayed in film versions as very elderly, Dickens's own notes indicate that she is only in her mid-thirties at the start of the novel. However, it is indicated in the novel that her long seclusion without sunlight has aged her. She is one of the most gothic characters in the work of Dickens.


title: Miss Havisham

text: Miss Havisham's father was a wealthy brewer and her mother died shortly after she was born. Her father remarried and had an illegitimate son, Arthur, with the household cook. Miss Havisham's relationship with her half-brother was a strained one.


title: Miss Havisham

text: She inherited most of her father's fortune and fell in love with a man named Compeyson, who conspired with the jealous Arthur to swindle her of her riches. Her cousin, Matthew Pocket, warned her to be careful, but she was too much in love to listen. On the wedding day, while she was dressing, Miss Havisham received a letter from Compeyson and realised he had defrauded her and she had been left at the altar.


title: Miss Havisham

text: Humiliated and heartbroken, Miss Havisham suffered a mental breakdown and remained alone in her decaying mansion Satis House – never removing her wedding dress, wearing only one shoe, leaving the wedding breakfast and cake uneaten on the table, and allowing only a few people to see her. She also had the clocks in her mansion stopped at twenty minutes to nine: the exact time when she had received Compeyson's letter.


title: Miss Havisham

text: While Miss Havisham's original goal was to prevent Estella from suffering as she had at the hands of a man, it changed as Estella grew older:


title: Miss Havisham

text: Miss Havisham repents late in the novel when Estella leaves to marry Pip's rival, Bentley Drummle; and she realises that she has caused Pip's heart to be broken in the same manner as her own; rather than achieving any kind of personal revenge, she has only caused more pain. Miss Havisham begs Pip for forgiveness.


title: Miss Havisham

text: After Pip leaves, Miss Havisham's dress catches on fire from her fireplace. Pip rushes back in and saves her. However, she has suffered severe burns to the front of her torso (she is laid on her back), up to the throat. The last words she speaks in the novel are (in a delirium) to Pip, referencing both Estella and a note she, Miss Havisham, has given him with her signature: "Take the pencil and write under my name, 'I forgive her!'"


title: Miss Havisham

text: A surgeon dresses her burns, and says that they are "far from hopeless". However, despite rallying for a time, she dies a few weeks later, leaving Estella as her chief beneficiary, and a considerable sum to Herbert Pocket's father, as a result of Pip's reference.


title: Miss Havisham

text: Eliza Emily Donnithorne (1821–1886) of Newtown, Sydney, was said to have been jilted by her groom on her wedding day and spent the rest of her life in a darkened house, her rotting wedding cake left as it was on the table, and with her front door kept permanently ajar in case her groom ever returned. She was widely considered at the time to be Dickens' model for Miss Havisham, although this cannot be proven.


title: Miss Havisham

text: In the 1965 Penguin edition, Angus Calder notes at Chapter 8 that "James Payn, a minor novelist, claimed to have given Dickens the idea for Miss Havisham – from a living original of his acquaintance. He declared that Dickens's account was 'not one whit exaggerated'." It is documented Dickens encountered a wealthy recluse called Elizabeth Parker on whom it is widely believed he based the character, whilst staying in Newport, Shropshire, at the aptly named Havisham Court.


title: Miss Havisham

text: Margaret Catherine Dick (1827—1879) of Bonchurch, Isle of Wight, was the daughter of Captain Samuel Dick, who lived in “Uppermount” Bonchurch. Dickens spent the summer of 1849 in Bonchurch writing chapters of David Copperfield, and based the character Mr Dick (who boarded with Miss Betsy Trotwood) on Margaret’s brother Charles George Dick who regularly walked with Dickens up St Boniface Down. Margaret Dick was jilted at the altar in 1860 and lived a reclusive life afterwards in Bonchurch. Dickens daughters , and estranged wife also visited Bonchurch in 1860, shortly after this event, and based the character Miss Havisham on Margaret Dick ; another villager Catherine Fane Haviland, could have been the clue to the name Miss Havisham.


title: Miss Havisham

text: "Miss Havisham's Fire" (1979, revised 2001) is an opera composed by Dominick Argento with a libretto by John Olon-Scrymgeour, based on Dickens' character. The entire story is told in flashback during an inquiry into Miss Havisham's death. The opera gives her first name as "Aurelia".


title: Miss Havisham

text: Ronald Frame's 2013 novel, "Havisham", is a non-canonical story about Miss Havisham's early life. The story tells how Miss Havisham (given the name of Catherine) is the daughter of a brewer. The story tells of more than just the infamous trauma of being left behind by her fiancé and goes on with her taking charge of her family's business before descending into vengeful madness, adopting Estella, and arranging the meeting of Estella and Pip.


title: Miss Havisham

text: Both "Sunset Boulevard" and "What Ever Happened to Baby Jane?" were inspired by David Lean's adaptation of "Great Expectations", as were, by extension, the characters of Norma Desmond and Baby Jane Hudson, and their homes.


title: Miss Havisham

text: In film adaptations of "Great Expectations", Miss Havisham has been played by a number of actors, including:


title: Miss Havisham

text: The condition of the "Miss Havisham effect" has been coined by scientists to describe a person who suffers a painful longing for lost love, which can become a physically addictive pleasure by activation of reward and pleasure centres in the brain, which have been identified to regulate addictive behaviour – regions commonly known to be responsible for craving and drug, alcohol and gambling addiction.


title: Oshkosh M-ATV

text: The Oshkosh M-ATV is a Mine-Resistant Ambush Protected (MRAP) vehicle developed by the Oshkosh Corporation for the MRAP All Terrain Vehicle (M-ATV) program. Intended to replace M1114 HMMWVs (Humvee), it is designed to provide the same levels of protection as the larger and heavier previous MRAPs, but with improved mobility.


title: Oshkosh M-ATV

text: In the summer of 2008, the U.S. Department of Defense (DoD) began to examine the possibility of developing and procuring a lighter-weight, all-terrain capable MRAP variant to address the poor roads and difficult terrain of Afghanistan. Source selection activity considered responses from more than 20 companies to a Request for Information (RFI)/market survey dated 21 August 2008 and in mid-November 2008 the U.S. government issued a pre-solicitation for an M-ATV. In early December 2008 the M-ATV formal Request for Proposals (RFP) was issued. The original M-ATV program requirement was for between 372 and 10,000 vehicles, with the most probable production quantity stated as 2,080.


title: Oshkosh M-ATV

text: In March 2009, it became known that two each of six different vehicle types (from five manufacturers) had been delivered to the U.S. Army for two months of evaluation, at the conclusion of which up to five ID/IQ (Indefinite Delivery/Indefinite Quantity) contracts would be awarded. In addition to Oshkosh's proposal, BAE Systems submitted two proposals: a Joint Light Tactical Vehicle (JLTV) derived design and an FMTV-based Caiman derivative. Force Dynamics (a Force Protection/General Dynamics Land Systems (GDLS) joint venture) offered the Cheetah, GDLS-C (Canada) offered an RG-31 MRAP derivative, and Navistar offered an MXT-based solution.


title: Oshkosh M-ATV

text: After GDLS-C's RG-31 was eliminated from the competition in May 2009, it was announced that the five remaining bidders had been awarded ID/IQ contracts, and were each to deliver three production-ready test vehicles for the next stage of the competition. At the completion of testing, the U.S. DoD stated that it planned to select a single M-ATV producer but could, at its discretion, place production orders with multiple producers as it had done with the initial MRAP procurement. On 30 June 2009, the M-ATV contract award was announced with a single ID/IQ contract award to Oshkosh. Brigadier General Michael Brogan, United States Marine Corps program officer for MRAP, stated that the Oshkosh M-ATV was chosen because it had the best survivability and Oshkosh had the best technical and manufacturing capabilities of all the competitors. The Oshkosh bid was also the second cheapest.


title: Oshkosh M-ATV

text: The initial M-ATV delivery order was valued at over $1 billion and included 2,244 M-ATVs. The overall M-ATV requirement had increased in early June from 2,080 to 5,244 M-ATVs, these split 2,598 (Army), 1,565 (Marines), 643 (U.S. Special Operations Command), 280 (Air Force), 65 (Navy), and 93 for testing.


title: Oshkosh M-ATV

text: In July 2009, the first 46 M-ATVs were delivered, and in November the 1,000th M-ATV was handed over. Oshkosh reached its contractual obligation to produce 1,000 M-ATVs per month ahead of schedule in December 2009, and by using its existing manufacturing facilities in Oshkosh, WI (50%), and making use of its recession-hit JLG telescopic handler facility in McConnellsburg, PA (50%). The first vehicles arrived in Afghanistan in October 2009 and were to be all delivered by March 2010.


title: Oshkosh M-ATV

text: In total 8,722 M-ATVs were delivered to the U.S. Army, U.S. Marine Corps, U.S. Air Force, and U.S. Special Operations Command (SOCOM). M-ATVs were delivered in two main variants. The base model is designated M1240 with the Objective Gunner Protection Kit [OGPK] manned turret; it is designated M1240A1 when fitted with the Underbody Improvement Kit (UIK). The second main variant is designated M1277 and is fitted with M153 CROWS remote-controlled weapon station (RCWS). Produced in smaller numbers, the SOCOM-specific variant is designated M1245; M1245A1 with UIK fitted.


title: Oshkosh M-ATV

text: As part of the overall divestiture of the MRAP fleet, the U.S. Government will keep about 80% (around 7,000) of the M-ATV fleet, 5,651 of these (inc. 250 for SOCOM) to be retained by the Army. Work is currently underway at Oshkosh's Wisconsin facility and the Red River Army Depot to reset the around 7,000 M-ATVs retained to a common build standard. Oshkosh was awarded an initial 500-vehicle M-ATV Reset contract in August 2014. Three additional contract options for 100 vehicles each were awarded in December 2014. Total contract value is in excess of US$77 million. Deliveries were scheduled to continue through September 2015.


title: Oshkosh M-ATV

text: Reset work centers on returning vehicles to Low Rate Initial Production (LRIP) 22 standard: essentially the build standard for the final M-ATV production batch. LRIP 22 includes upgrades such as the UIK and enhanced Automatic Fire Extinguishing System (AFES). Reset work also adds Engineering Change Proposals (ECPs) that include acoustic signature reduction (muffler), Modular Ammunition Restraint System (MARS) ammunition storage, and some Government Furnished Equipment (GFE) relocation.


title: Oshkosh M-ATV

text: On 28 May 2015, Oshkosh announced the U.S. Army had awarded it a contract modification for the reset of 360 additional M-ATVs. The modification includes options for the reset of up to 1,440 additional M-ATVs. Deliveries for this latest modification started October 2015. Oshkosh is on contract to reset a combined 1,160 M-ATVs with a total value of over $115 million.


title: Oshkosh M-ATV

text: In January 2017, the US Marine Corps disclosed that they would upgrade and refurbish around 80 M-ATVs over a five-month period, the work scheduled to take three to four weeks for each M-ATV and cost around $385,000 per vehicle, with both Marine and Air Force M-ATVs involved. The main difference between the two services M-ATVs is the armament; Air Force M-ATVs are fitted with a CROWS (Common Remotely Operated Weapon Station), while Marine M-ATVs are fitted with a manual OGPK (Objective Gunner Protection Kit) turret.


title: Oshkosh M-ATV

text: At the Association for Unmanned Vehicle Systems International (AUVSI) 2013 convention, Oshkosh announced the integration of the TerraMax system onto the M-ATV to allow the type to be converted into an unmanned ground vehicle. The goal is to use the M-ATV as an unmanned platform for route clearance and counter improvised explosive device (IED) missions by engineers.


title: Oshkosh M-ATV

text: Oshkosh Defense unveiled the M-ATV Extended Wheel Base Medical (EXM) variant at the International Defense Exhibition and Conference (IDEX) 2015 (22–26 Feb.) in Abu Dhabi, United Arab Emirates. This variant of the M-ATV has enough interior capacity to simultaneously transport two litter-bound patients, two ambulatory patients, a medic, commander and driver. The M-ATV EXM's customizable internal configuration also enables equipment to be accessed quickly by a centrally positioned medic.


title: Oshkosh M-ATV

text: In February 2015, Oshkosh Defense and Alliant Techsystems conducted a firing demonstration of the M230LF 30 mm chain gun on an M-ATV to demonstrate the viability and effectiveness of a medium caliber weapon system for light tactical vehicles. The live fire demonstration showcased improved accuracy in mobile engagements and improved lethality on the M-ATV using the gun, mounted on the R400S-Mk2, a 3-axis stabilized remote weapon station weighing less than . The addition of the M230LF stabilized on the RWS provides mobile precise lethality, usually reserved for heavier combat vehicles, with exceptional off-road mobility and MRAP levels of protection.


title: Oshkosh M-ATV

text: The M-ATV proved to be more survivable than the Humvee and was lighter than other MRAP versions, but to further enhance survivability and mobility for troops, the U.S. military undertook the Joint Light Tactical Vehicle (JLTV) program to obtain a vehicle combining light weight, mobility, and protection. In August 2015, Oshkosh was awarded the contract for their Light Combat Tactical All-Terrain Vehicle (L-ATV), which took design lessons from fielding the M-ATV and incorporated them into a truck at two-thirds the weight and with faster off-road speeds.


title: Oshkosh M-ATV

text: By 2018, the Marine Corps was deploying a Counter-Unmanned Aerial System (C-UAS) that can be mounted onto an M-ATV. The Ground-Based Air Defense (GBAD) Counter-UAS system consists of the RPS-42 S-band radar, the Modi electronic warfare system, visual sensors and Raytheon Coyote anti-drone UAV to detect, track and destroy hostile drones.


title: Oshkosh M-ATV

text: The M-ATV combines a Plasan designed armored hull developed for the Northrop Grumman/Oshkosh JLTV Technology Development (TD) phase proposal with some elements of the Medium Tactical Vehicle Replacement (MTVR) chassis and Oshkosh's TAK-4 suspension system. TAK-4 suspension is coil sprung and fully independent, and offers 16 inches of wheel travel.


title: Oshkosh M-ATV

text: For survivability, and in addition to the V-shaped hull which is optimized for IED protection, other aids include the ability to take a 7.62 mm round to the engine oil/coolant/hydraulic system and continue to drive for at least one kilometer. The engine compartment is also protected with the Stat-X engine fire suppression system. A central tire inflation system (CTIS) and run-flat inserts allow the M-ATV to travel at least 30 miles at 30 mph even if two tires lose pressure. The M-ATV also features a traction control system and anti-lock brakes.


title: Oshkosh M-ATV

text: Armament is roof-mounted and can be either manually or remotely operated. Manual options include a M240 machine gun, a Mk 19 grenade launcher, an M2 Browning machine gun, a MILAN anti-tank guided missile, or a BGM-71 TOW anti-tank guided missile launcher. Remote option is usually the CROWS (Common Remotely Operated Weapon Station), however as previously mentioned, Oshkosh has also fitted for demonstration purposes the R400S-Mk2, a 3-axis stabilized remote weapon station when has the M230LF chain autocannon mounted on.


title: Oshkosh M-ATV

text: Other M-ATV features include a HVAC system and power outlets for charging portable electronic devices. The M-ATV is also unique among MRAP-type designs in that it uses suicide-type rear doors.


title: Oshkosh M-ATV

text: The United Arab Emirates Army initially ordered 55 M-ATVs through an FMS sale in 2011. The UAE ordered another 750 M-ATVs direct from Oshkosh in July 2012. These are to provide greater off-road mobility and crew protection for regional security and peace-keeping operations; users include the elite Presidential Guard. Deliveries were completed in August 2013. In September 2014, the UAE requested another 44 M-ATVs from U.S. surplus stocks.


title: Oshkosh M-ATV

text: In September 2013, the Saudi Arabian Army began negotiations for an order for an undisclosed number of M-ATVs. Saudi Arabia received an estimated 450 M-ATVs including some extended wheelbase variants.


title: Oshkosh M-ATV

text: On 7 April 2014, the U.S. government donated 162 M-ATVs to the Croatian Army for use in small-scale combat operations in urban and restricted environments. Fifteen M-ATVs are going to the Croatian Special Forces Command (SFCOM), five will be with the Support Command (SCOM), two with the Military Police Regiment, and 78 entered service with the Croatian Army in 2015, with a further 62 to follow in 2016 for the 1st Battalion of the Motorized Guards Brigade in Gospic.


title: Oshkosh M-ATV

text: In January 2015, it was reported that the U.S. was to donate 308 Mine Resistant Ambush Protected (MRAP) vehicles to Uzbekistan under the Excess Defense Articles program. Requested totals include 159 M-ATVs with UIK, plus 50 Maxxpro Plus, 20 MaxxPro recovery, 50 BAE RG-33L CAT II and 70 Cougar CAT 1 (W/ISS (65); W/O ISS 5) vehicles.


title: Oshkosh M-ATV

text: In February 2015, it was disclosed that the U.S. was providing 20 M-ATVs to African Union (AU) peacekeepers in Somalia. These M-ATVs will replace older 1980s-vintage Casspir vehicles.


title: Oshkosh M-ATV

text: On 25 February 2015, Polish special forces received 45 M-ATVs. The handover ceremony took place in Cracow, Poland and the US Ambassador in Poland, Stephen D. Mull, participated in the event. Delivery of the MRAP vehicles was carried out within the framework of the Excess Defense Articles program, the standard way that the U.S. military gives surplus equipment to allies.


title: Oshkosh M-ATV

text: In June 2016, photographs released by the Iraqi Ministry of Defence showed M-ATVs with Iraqi Special Operations Forces (ISOF) (also known as the Counter-Terrorism Service (CTS)) units advancing northwards for the operation to retake the Islamic State-held city of Mosul.


title: Oshkosh M-ATV

text: Oshkosh formally announced the addition of designated variants to the M-ATV family in April 2014. The range has evolved since then, the current five variants announced in May 2016.


title: Oshkosh M-ATV

text: In October 2015, Oshkosh unveiled an M-ATV 6×6-wheeled technology demonstrator. The vehicle was designed with greater interior volume to transport three crew and 8–12 troops and to have greater payload capacity while maintaining MRAP-level protection and off-road mobility, combining the TAK-4 independent suspension and the M-ATV 6×6's all-wheel steer for maneuverability across any terrain. Top speed is with a 70 percent off-road/30 percent on-road suspension durability profile. It has a curb weight of 21 tons (), a payload capacity of , and the same turning radius as the 4x4 version.


title: Strabo

text: Strabo (; "Strábōn"; 64 or 63 BC 24 AD) was a Greek geographer, philosopher, and historian who lived in Asia Minor during the transitional period of the Roman Republic into the Roman Empire.


title: Strabo

text: Strabo was born to an affluent family from Amaseia in Pontus (in present-day Turkey) in around 64BC. His family had been involved in politics since at least the reign of Mithridates V. Strabo was related to Dorylaeus on his mother's side. Several other family members, including his paternal grandfather had served Mithridates VI during the Mithridatic Wars. As the war drew to a close, Strabo's grandfather had turned several Pontic fortresses over to the Romans. Strabo wrote that "great promises were made in exchange for these services", and as Persian culture endured in Amaseia even after Mithridates and Tigranes were defeated, scholars have speculated about how the family's support for Rome might have affected their position in the local community, and whether they might have been granted Roman citizenship as a reward.


title: Strabo

text: Strabo's life was characterized by extensive travels. He journeyed to Egypt and Kush, as far west as coastal Tuscany and as far south as Ethiopia in addition to his travels in Asia Minor and the time he spent in Rome. Travel throughout the Mediterranean and Near East, especially for scholarly purposes, was popular during this era and was facilitated by the relative peace enjoyed throughout the reign of Augustus (27 BC – AD 14). He moved to Rome in 44 BC, and stayed there, studying and writing, until at least 31 BC. In 29 BC, on his way to Corinth (where Augustus was at the time), he visited the island of Gyaros in the Aegean Sea. Around 25 BC, he sailed up the Nile until he reached Philae, after which point there is little record of his travels until AD 17.


title: Strabo

text: It is not known precisely when Strabo's "Geography" was written, though comments within the work itself place the finished version within the reign of Emperor Tiberius. Some place its first drafts around 7 BC, others around AD 17 or AD 18. The latest passage to which a date can be assigned is his reference to the death in AD 23 of Juba II, king of Maurousia (Mauretania), who is said to have died "just recently". He probably worked on the "Geography" for many years and revised it steadily, but not always consistently. It is an encyclopaedic chronicle and consists of political, economic, social, cultural, geographic description covering almost all of Europe and the Mediterranean: British Isles, Iberian Peninsula, Gaul, Germania, the Alps, Italy, Greece, Northern Black Sea region, Anatolia, Middle East, Central Asia and North Africa. The "Geography" is the only extant work providing information about both Greek and Roman peoples and countries during the reign of Augustus.


title: Strabo

text: On the presumption that "recently" means within a year, Strabo stopped writing that year or the next (AD 24), at which time he is thought to have died. He was influenced by Homer, Hecataeus and Aristotle. The first of Strabo's major works, "Historical Sketches" ("Historica hypomnemata"), written while he was in Rome (c. 20 BC), is nearly completely lost. Meant to cover the history of the known world from the conquest of Greece by the Romans, Strabo quotes it himself and other classical authors mention that it existed, although the only surviving document is a fragment of papyrus now in the possession of the University of Milan (renumbered [Papyrus] 46).


title: Strabo

text: Strabo studied under several prominent teachers of various specialities throughout his early life at different stops during his Mediterranean travels. The first chapter of his education took place in Nysa (modern Sultanhisar, Turkey) under the master of rhetoric Aristodemus, who had formerly taught the sons of the Roman general who had taken over Pontus. Aristodemus was the head of two schools of rhetoric and grammar, one in Nysa and one in Rhodes. The school in Nysa possessed a distinct intellectual curiosity in Homeric literature and the interpretation of the ancient Greek epics. Strabo was an admirer of Homer's poetry, perhaps as a consequence of his time spent in Nysa with Aristodemus.


title: Strabo

text: At around the age of 21, Strabo moved to Rome, where he studied philosophy with the Peripatetic Xenarchus, a highly respected tutor in Augustus's court. Despite Xenarchus's Aristotelian leanings, Strabo later gives evidence to have formed his own Stoic inclinations. In Rome, he also learned grammar under the rich and famous scholar Tyrannion of Amisus. Although Tyrannion was also a Peripatetic, he was more relevantly a respected authority on geography, a fact of some significance considering Strabo's future contributions to the field.


title: Strabo

text: The final noteworthy mentor to Strabo was Athenodorus Cananites, a philosopher who had spent his life since 44 BC in Rome forging relationships with the Roman elite. Athenodorus passed onto Strabo his philosophy, his knowledge and his contacts. Unlike the Aristotelian Xenarchus and Tyrannion who preceded him in teaching Strabo, Athenodorus was a Stoic and almost certainly the source of Strabo's diversion from the philosophy of his former mentors. Moreover, from his own first-hand experience, Athenodorus provided Strabo with information about regions of the empire which Strabo would not otherwise have known about.


title: Strabo

text: Strabo is best known for his work "Geographica" ("Geography"), which presented a descriptive history of people and places from different regions of the world known during his lifetime.


title: Strabo

text: Although the "Geographica" was rarely utilized by contemporary writers, a multitude of copies survived throughout the Byzantine Empire. It first appeared in Western Europe in Rome as a Latin translation issued around 1469. The first Greek edition was published in 1516 in Venice. Isaac Casaubon, classical scholar and editor of Greek texts, provided the first critical edition in 1587.


title: Strabo

text: Although Strabo cited the classical Greek astronomers Eratosthenes and Hipparchus, acknowledging their astronomical and mathematical efforts covering geography, he claimed that a descriptive approach was more practical, such that his works were designed for statesmen who were more anthropologically than numerically concerned with the character of countries and regions.


title: Strabo

text: As such, "Geographica" provides a valuable source of information on the ancient world of his day, especially when this information is corroborated by other sources. He travelled extensively, as he says: "Westward I have journeyed to the parts of Etruria opposite Sardinia; towards the south from the Euxine to the borders of Ethiopia; and perhaps not one of those who have written geographies has visited more places than I have between those limits."


title: Strabo

text: It is not known when he wrote "Geographica", but he spent much time in the famous library in Alexandria taking notes from "the works of his predecessors". A first edition was published in 7 BC and a final edition no later than 23 AD, in what may have been the last year of Strabo's life. It took some time for "Geographica" to be recognized by scholars and to become a standard.


title: Strabo

text: Alexandria itself features extensively in the last book of "Geographica", which describes it as a thriving port city with a highly developed local economy. Strabo notes the city's many beautiful public parks, and its network of streets wide enough for chariots and horsemen. "Two of these are exceeding broad, over a plethron in breadth, and cut one another at right angles ... All the buildings are connected one with another, and these also with what are beyond it."


title: Strabo

text: Lawrence Kim observes that Strabo is "... pro-Roman throughout the Geography. But while he acknowledges and even praises Roman ascendancy in the political and military sphere, he also makes a significant effort to establish Greek primacy over Rome in other contexts."


title: Strabo

text: In Europe, Strabo was the first to connect the Danube – Danouios and the Istros – with the change of names occurring at "the cataracts," the modern Iron Gates on the Romanian/Serbian border.


title: Strabo

text: In India, a country he never visited, Strabo described small flying reptiles that were long with a snake-like body and bat-like wings (this description matches the Indian flying lizard "Draco dussumieri"), winged scorpions, and other mythical creatures along with those that were actually factual. Other historians, such as Herodotus, Aristotle, and Flavius Josephus, mentioned similar creatures.


title: Strabo

text: Strabo commented on fossil formation mentioning Nummulite (quoted from Celâl Şengör):One extraordinary thing which I saw at the pyramids must not be omitted. Heaps of stones from the quarries lie in front of the pyramids. Among these are found pieces which in shape and size resemble lentils. Some contain substances like grains half peeled. These, it is said, are the remnants of the workmen's food converted into stone; which is not probable. For at home in our country (Amaseia), there is a long hill in a plain, which abounds with pebbles of a porous stone, resembling lentils. The pebbles of the sea-shore and of rivers suggest somewhat of the same difficulty [respecting their origin]; some explanation may indeed be found in the motion [to which these are subject] in flowing waters, but the investigation of the above fact presents more difficulty. I have said elsewhere, that in sight of the pyramids, on the other side in Arabia, and near the stone quarries from which they are built, is a very rocky mountain, called the Trojan mountain; beneath it there are caves, and near the caves and the river a village called Troy, an ancient settlement of the captive Trojans who had accompanied Menelaus and settled there.


title: Strabo

text: Strabo commented on volcanism (effusive eruption) which he observed at Katakekaumene (modern Kula, Western Turkey). Strabo's observations predated Pliny the Younger who witnessed the eruption of Mount Vesuvius on 24 August AD 79 in Pompeii:…There are no trees here, but only the vineyards where they produce the Katakekaumene wines which are by no means inferior from any of the wines famous for their quality. The soil is covered with ashes, and black in colour as if the mountainous and rocky country was made up of fires. Some assume that these ashes were the result of thunderbolts and subterranean explosions, and do not doubt that the legendary story of Typhon takes place in this region. Ksanthos adds that the king of this region was a man called Arimus. However, it is not reasonable to accept that the whole country was burned down at a time as a result of such an event rather than as a result of a fire bursting from underground whose source has now died out. Three pits are called "Physas" and separated by forty stadia from each other. Above these pits, there are hills formed by the hot masses burst out from the ground as estimated by a logical reasoning. Such type of soil is very convenient for viniculture, just like the Katanasoil which is covered with ashes and where the best wines are still produced abundantly. Some writers concluded by looking at these places that there is a good reason for calling Dionysus by the name ("Phrygenes").


title: Scheme (programming language)

text: Scheme is a dialect of the Lisp family of programming languages. Scheme was created during the 1970s at the MIT AI Lab and released by its developers, Guy L. Steele and Gerald Jay Sussman, via a series of memos now known as the Lambda Papers. It was the first dialect of Lisp to choose lexical scope and the first to require implementations to perform tail-call optimization, giving stronger support for functional programming and associated techniques such as recursive algorithms. It was also one of the first programming languages to support first-class continuations. It had a significant influence on the effort that led to the development of Common Lisp.


title: Scheme (programming language)

text: The Scheme language is standardized in the official IEEE standard and a "de facto" standard called the "Revised Report on the Algorithmic Language Scheme" (R"n"RS). A widely implemented standard is R5RS (1998). The most recently ratified standard of Scheme is "R7RS-small" (2013). The more expansive and modular R6RS was ratified in 2007. Both trace their descent from R5RS; the timeline below reflects the chronological order of ratification.


title: Scheme (programming language)

text: Scheme started in the 1970s as an attempt to understand Carl Hewitt's Actor model, for which purpose Steele and Sussman wrote a "tiny Lisp interpreter" using Maclisp and then "added mechanisms for creating actors and sending messages". Scheme was originally called "Schemer", in the tradition of other Lisp-derived languages such as Planner or "Conniver". The current name resulted from the authors' use of the ITS operating system, which limited filenames to two components of at most six characters each. Currently, "Schemer" is commonly used to refer to a Scheme programmer.


title: Scheme (programming language)

text: A new language standardization process began at the 2003 Scheme workshop, with the goal of producing an R6RS standard in 2006. This process broke with the earlier R"n"RS approach of unanimity.


title: Scheme (programming language)

text: R6RS features a standard module system, allowing a split between the core language and libraries. A number of drafts of the R6RS specification were released, the final version being R5.97RS. A successful vote resulted in the ratification of the new standard, announced on August 28, 2007.


title: Scheme (programming language)

text: Currently the newest releases of various Scheme implementations support the R6RS standard. There is a portable reference implementation of the proposed implicitly phased libraries for R6RS, called psyntax, which loads and bootstraps itself properly on various older Scheme implementations.


title: Scheme (programming language)

text: A feature of R6RS is the record-type descriptor (RTD). When an RTD is created and used, the record type representation can show the memory layout. It also calculated object field bit mask and mutable Scheme object field bit masks, and helped the garbage collector know what to do with the fields without traversing the whole fields list that are saved in the RTD. RTD allows users to expand the basic RTD to create a new record system.


title: Scheme (programming language)

text: R6RS introduces numerous significant changes to the language. The source code is now specified in Unicode, and a large subset of Unicode characters may now appear in Scheme symbols and identifiers, and there are other minor changes to the lexical rules. Character data is also now specified in Unicode. Many standard procedures have been moved to the new standard libraries, which themselves form a large expansion of the standard, containing procedures and syntactic forms that were formerly not part of the standard. A new module system has been introduced, and systems for exception handling are now standardized. Syntax-rules has been replaced with a more expressive syntactic abstraction facility (syntax-case) which allows the use of all of Scheme at macro expansion time. Compliant implementations are now "required" to support Scheme's full numeric tower, and the semantics of numbers have been expanded, mainly in the direction of support for the IEEE 754 standard for floating point numerical representation.


title: Scheme (programming language)

text: The R6RS standard has caused controversy because some see it as a departure from the minimalist philosophy. In August 2009, the Scheme Steering Committee, which oversees the standardization process, announced its intention to recommend splitting Scheme into two languages: a large modern programming language for programmers; and a small version, a subset of the large version retaining the minimalism praised by educators and casual implementors. Two working groups were created to work on these two new versions of Scheme. The Scheme Reports Process site has links to the working groups' charters, public discussions and issue tracking system.


title: Scheme (programming language)

text: The ninth draft of R7RS (small language) was made available on April 15, 2013. A vote ratifying this draft closed on May 20, 2013, and the final report has been available since August 6, 2013, describing "the 'small' language of that effort: therefore it cannot be considered in isolation as the successor to R6RS".


title: Scheme (programming language)

text: Scheme is primarily a functional programming language. It shares many characteristics with other members of the Lisp programming language family. Scheme's very simple syntax is based on s-expressions, parenthesized lists in which a prefix operator is followed by its arguments. Scheme programs thus consist of sequences of nested lists. Lists are also the main data structure in Scheme, leading to a close equivalence between source code and data formats (homoiconicity). Scheme programs can easily create and evaluate pieces of Scheme code dynamically.


title: Scheme (programming language)

text: The reliance on lists as data structures is shared by all Lisp dialects. Scheme inherits a rich set of list-processing primitives such as codice_1, codice_2 and codice_3 from its Lisp progenitors. Scheme uses strictly but dynamically typed variables and supports first class procedures. Thus, procedures can be assigned as values to variables or passed as arguments to procedures.


title: Scheme (programming language)

text: This section concentrates mainly on innovative features of the language, including those features that distinguish Scheme from other Lisps. Unless stated otherwise, descriptions of features relate to the R5RS standard. In examples provided in this section, the notation "===> result" is used to indicate the result of evaluating the expression on the immediately preceding line. This is the same convention used in R5RS.


title: Scheme (programming language)

text: Scheme is a very simple language, much easier to implement than many other languages of comparable expressive power. This ease is attributable to the use of lambda calculus to derive much of the syntax of the language from more primitive forms. For instance of the 23 s-expression-based syntactic constructs defined in the R5RS Scheme standard, 14 are classed as derived or library forms, which can be written as macros involving more fundamental forms, principally lambda. As R5RS (§3.1) says: "The most fundamental of the variable binding constructs is the lambda expression, because all other variable binding constructs can be explained in terms of lambda expressions."


title: Scheme (programming language)

text: Example: a macro to implement codice_4 as an expression using codice_5 to perform the variable bindings.


title: Scheme (programming language)

text: Thus using codice_4 as defined above a Scheme implementation would rewrite "codice_7" as "codice_8", which reduces implementation's task to that of coding procedure instantiations.


title: Scheme (programming language)

text: In 1998, Sussman and Steele remarked that the minimalism of Scheme was not a conscious design goal, but rather the unintended outcome of the design process. "We were actually trying to build something complicated and discovered, serendipitously, that we had accidentally designed something that met all our goals but was much simpler than we had intended...we realized that the lambda calculus—a small, simple formalism—could serve as the core of a powerful and expressive programming language."


title: Scheme (programming language)

text: Like most modern programming languages and unlike earlier Lisps such as Maclisp, Scheme is lexically scoped: all possible variable bindings in a program unit can be analyzed by reading the text of the program unit without consideration of the contexts in which it may be called. This contrasts with dynamic scoping which was characteristic of early Lisp dialects, because of the processing costs associated with the primitive textual substitution methods used to implement lexical scoping algorithms in compilers and interpreters of the day. In those Lisps, it was perfectly possible for a reference to a free variable inside a procedure to refer to quite distinct bindings external to the procedure, depending on the context of the call.


title: Scheme (programming language)

text: The impetus to incorporate lexical scoping, which was an unusual scoping model in the early 1970s, into their new version of Lisp, came from Sussman's studies of ALGOL. He suggested that ALGOL-like lexical scoping mechanisms would help to realize their initial goal of implementing Hewitt's Actor model in Lisp.


title: Scheme (programming language)

text: The key insights on how to introduce lexical scoping into a Lisp dialect were popularized in Sussman and Steele's 1975 Lambda Paper, "Scheme: An Interpreter for Extended Lambda Calculus", where they adopted the concept of the lexical closure (on page 21), which had been described in an AI Memo in 1970 by Joel Moses, who attributed the idea to Peter J. Landin.


title: Scheme (programming language)

text: Alonzo Church's mathematical notation, the lambda calculus, has inspired Lisp's use of "lambda" as a keyword for introducing a procedure, as well as influencing the development of functional programming techniques involving the use of higher-order functions in Lisp. But early Lisps were not suitable expressions of the lambda calculus because of their treatment of free variables.


title: Scheme (programming language)

text: A formal lambda system has axioms and a complete calculation rule. It is helpful for the analysis using mathematical logic and tools. In this system, calculation can be seen as a directional deduction. The syntax of lambda calculus follows the recursive expressions from x, y, z, ...,parentheses, spaces, the period and the symbol λ. The function of lambda calculation includes: First, serve as a starting point of powerful mathematical logic. Second, it can reduce the requirement of programmers to consider the implementation details, because it can be used to imitate machine evaluation. Finally, the lambda calculation created a substantial meta-theory.


title: Scheme (programming language)

text: The introduction of lexical scope resolved the problem by making an equivalence between some forms of lambda notation and their practical expression in a working programming language. Sussman and Steele showed that the new language could be used to elegantly derive all the imperative and declarative semantics of other programming languages including ALGOL and Fortran, and the dynamic scope of other Lisps, by using lambda expressions not as simple procedure instantiations but as "control structures and environment modifiers". They introduced continuation-passing style along with their first description of Scheme in the first of the Lambda Papers, and in subsequent papers, they proceeded to demonstrate the raw power of this practical use of lambda calculus.


title: Scheme (programming language)

text: Scheme inherits its block structure from earlier block structured languages, particularly ALGOL. In Scheme, blocks are implemented by three "binding constructs": codice_4, codice_10 and codice_11. For instance, the following construct creates a block in which a symbol called codice_12 is bound to the number 10:


title: Scheme (programming language)

text: Blocks can be nested to create arbitrarily complex block structures according to the need of the programmer. The use of block structuring to create local bindings alleviates the risk of namespace collision that can otherwise occur.


title: Scheme (programming language)

text: One variant of codice_4, codice_10, permits bindings to refer to variables defined earlier in the same construct, thus:


title: Scheme (programming language)

text: The other variant, codice_11, is designed to enable mutually recursive procedures to be bound to one another.


title: Scheme (programming language)

text: All procedures bound in a single codice_11 may refer to one another by name, as well as to values of variables defined earlier in the same codice_11, but they may not refer to "values" defined later in the same codice_11.


title: Scheme (programming language)

text: A variant of codice_4, the "named let" form, has an identifier after the codice_4 keyword. This binds the let variables to the argument of a procedure whose name is the given identifier and whose body is the body of the let form. The body may be repeated as desired by calling the procedure. The named let is widely used to implement iteration.


title: Scheme (programming language)

text: Scheme has an iteration construct, codice_21, but it is more idiomatic in Scheme to use tail recursion to express iteration. Standard-conforming Scheme implementations are required to optimize tail calls so as to support an unbounded number of active tail calls (R5RS sec. 3.5)—a property the Scheme report describes as "proper tail recursion"—making it safe for Scheme programmers to write iterative algorithms using recursive structures, which are sometimes more intuitive. Tail recursive procedures and the "named codice_4" form provide support for iteration using tail recursion.


title: Scheme (programming language)

text: Continuations in Scheme are first-class objects. Scheme provides the procedure codice_23 (also known as codice_24) to capture the current continuation by packing it up as an escape procedure bound to a formal argument in a procedure provided by the programmer. (R5RS sec. 6.4) First-class continuations enable the programmer to create non-local control constructs such as iterators, coroutines, and backtracking.


title: Scheme (programming language)

text: Continuations can be used to emulate the behavior of return statements in imperative programming languages. The following function codice_25, given function codice_26 and list codice_27, returns the first element codice_28 in codice_27 such that codice_30 returns true.


title: Scheme (programming language)

text: The following example, a traditional programmer's puzzle, shows that Scheme can handle continuations as first-class objects, binding them to variables and passing them as arguments to procedures.


title: Scheme (programming language)

text: In contrast to Common Lisp, all data and procedures in Scheme share a common namespace, whereas in Common Lisp functions and data have separate namespaces making it possible for a function and a variable to have the same name, and requiring special notation for referring to a function as a value. This is sometimes known as the "Lisp-1 vs. Lisp-2" distinction, referring to the unified namespace of Scheme and the separate namespaces of Common Lisp.


title: Scheme (programming language)

text: In Scheme, the same primitives that are used to manipulate and bind data can be used to bind procedures. There is no equivalent of Common Lisp's codice_32 and codice_33 primitives.


title: Scheme (programming language)

text: This subsection documents design decisions that have been taken over the years which have given Scheme a particular character, but are not the direct outcomes of the original design.


title: Scheme (programming language)

text: Scheme specifies a comparatively full set of numerical datatypes including complex and rational types, which is known in Scheme as the numerical tower (R5RS sec. 6.2). The standard treats these as abstractions, and does not commit the implementor to any particular internal representations.


title: Scheme (programming language)

text: Numbers may have the quality of exactness. An exact number can only be produced by a sequence of exact operations involving other exact numbers—inexactness is thus contagious. The standard specifies that any two implementations must produce equivalent results for all operations resulting in exact numbers.


title: Scheme (programming language)

text: The R5RS standard specifies procedures codice_34 and codice_35 which can be used to change the exactness of a number. codice_35 produces "the exact number that is numerically closest to the argument". codice_34 produces "the inexact number that is numerically closest to the argument". The R6RS standard omits these procedures from the main report, but specifies them as R5RS compatibility procedures in the standard library (rnrs r5rs (6)).


title: Scheme (programming language)

text: In the R5RS standard, Scheme implementations are not required to implement the whole numerical tower, but they must implement "a coherent subset consistent with both the purposes of the implementation and the spirit of the Scheme language" (R5RS sec. 6.2.3). The new R6RS standard does require implementation of the whole tower, and "exact integer objects and exact rational number objects of practically unlimited size and precision, and to implement certain procedures...so they always return exact results when given exact arguments" (R6RS sec. 3.4, sec. 11.7.1).


title: Scheme (programming language)

text: Both implementations conform to the R5RS standard but the second does not conform to R6RS because it does not implement the full numerical tower.


title: Scheme (programming language)

text: The lexical context of the original definition of the promise is preserved, and its value is also preserved after the first use of codice_39. The promise is only ever evaluated once.


title: Scheme (programming language)

text: These primitives, which produce or handle values known as promises, can be used to implement advanced lazy evaluation constructs such as streams.


title: Scheme (programming language)

text: In the R6RS standard, these are no longer primitives, but instead, are provided as part of the R5RS compatibility library (rnrs r5rs (6)).


title: Scheme (programming language)

text: In R5RS, a suggested implementation of codice_38 and codice_39 is given, implementing the promise as a procedure with no arguments (a thunk) and using memoization to ensure that it is only ever evaluated once, irrespective of the number of times codice_39 is called (R5RS sec. 6.4).


title: Scheme (programming language)

text: SRFI 41 enables the expression of both finite and infinite sequences with extraordinary economy. For example, this is a definition of the fibonacci sequence using the functions defined in SRFI 41:


title: Scheme (programming language)

text: Most Lisps specify an order of evaluation for procedure arguments. Scheme does not. Order of evaluation—including the order in which the expression in the operator position is evaluated—may be chosen by an implementation on a call-by-call basis, and the only constraint is that "the effect of any concurrent evaluation of the operator and operand expressions is constrained to be consistent with some sequential order of evaluation." (R5RS sec. 4.1.3)


title: Scheme (programming language)

text: ev is a procedure that describes the argument passed to it, then returns the value of the argument. In contrast with other Lisps, the appearance of an expression in the operator position (the first item) of a Scheme expression is quite legal, as long as the result of the expression in the operator position is a procedure.


title: Scheme (programming language)

text: In calling the procedure "+" to add 1 and 2, the expressions (ev +), (ev 1) and (ev 2) may be evaluated in any order, as long as the effect is not as if they were evaluated in parallel. Thus the following three lines may be displayed in any order by standard Scheme when the above example code is executed, although the text of one line may not be interleaved with another because that would violate the sequential evaluation constraint.


title: Scheme (programming language)

text: In the R5RS standard and also in later reports, the syntax of Scheme can easily be extended via the macro system. The R5RS standard introduced a powerful hygienic macro system that allows the programmer to add new syntactic constructs to the language using a simple pattern matching sublanguage (R5RS sec 4.3). Prior to this, the hygienic macro system had been relegated to an appendix of the R4RS standard, as a "high level" system alongside a "low level" macro system, both of which were treated as extensions to Scheme rather than an essential part of the language.


title: Scheme (programming language)

text: Implementations of the hygienic macro system, also called codice_44, are required to respect the lexical scoping of the rest of the language. This is assured by special naming and scoping rules for macro expansion and avoids common programming errors that can occur in the macro systems of other programming languages. R6RS specifies a more sophisticated transformation system, codice_45, which has been available as a language extension to R5RS Scheme for some time.


title: Scheme (programming language)

text: Invocations of macros and procedures bear a close resemblance—both are s-expressions—but they are treated differently. When the compiler encounters an s-expression in the program, it first checks to see if the symbol is defined as a syntactic keyword within the current lexical scope. If so, it then attempts to expand the macro, treating the items in the tail of the s-expression as arguments without compiling code to evaluate them, and this process is repeated recursively until no macro invocations remain. If it is not a syntactic keyword, the compiler compiles code to evaluate the arguments in the tail of the s-expression and then to evaluate the variable represented by the symbol at the head of the s-expression and call it as a procedure with the evaluated tail expressions passed as actual arguments to it.


title: Scheme (programming language)

text: Most Scheme implementations also provide additional macro systems. Among popular ones are syntactic closures, explicit renaming macros and codice_46, a non-hygienic macro system similar to codice_47 system provided in Common Lisp.


title: Scheme (programming language)

text: The inability to specify whether or not a macro is hygienic is one of the shortcomings of the macro system. Alternative models for expansion such as scope sets provide a potential solution.


title: Scheme (programming language)

text: Prior to R5RS, Scheme had no standard equivalent of the codice_48 procedure which is ubiquitous in other Lisps, although the first Lambda Paper had described codice_49 as "similar to the LISP function EVAL" and the first Revised Report in 1978 replaced this with codice_50, which took two arguments. The second, third and fourth revised reports omitted any equivalent of codice_48.


title: Scheme (programming language)

text: The reason for this confusion is that in Scheme with its lexical scoping the result of evaluating an expression depends on where it is evaluated. For instance, it is not clear whether the result of evaluating the following expression should be 5 or 6:


title: Scheme (programming language)

text: If it is evaluated in the outer environment, where codice_52 is defined, the result is the sum of the operands. If it is evaluated in the inner environment, where the symbol "+" has been bound to the value of the procedure "*", the result is the product of the two operands.


title: Scheme (programming language)

text: R5RS resolves this confusion by specifying three procedures that return environments and providing a procedure codice_48 that takes an s-expression and an environment and evaluates the expression in the environment provided. (R5RS sec. 6.5) R6RS extends this by providing a procedure called codice_54 by which the programmer can specify exactly which objects to import into the evaluation environment.


title: Scheme (programming language)

text: With modern scheme (usually compatible with R5RS) to evaluate this expression, one needs to define a function codice_49 which can look like this:


title: Scheme (programming language)

text: In most dialects of Lisp including Common Lisp, by convention the value codice_57 evaluates to the value false in a boolean expression. In Scheme, since the IEEE standard in 1991, all values except codice_58, including codice_57's equivalent in Scheme which is written as codice_60, evaluate to the value true in a boolean expression. (R5RS sec. 6.3.1)


title: Scheme (programming language)

text: Where the constant representing the boolean value of true is codice_61 in most Lisps, in Scheme it is codice_62.


title: Scheme (programming language)

text: In Scheme the primitive datatypes are disjoint. Only one of the following predicates can be true of any Scheme object: codice_63, codice_64, codice_65, codice_66, codice_67, codice_68, codice_69, codice_70, codice_71. (R5RS sec 3.2)


title: Scheme (programming language)

text: Within the numerical datatype, by contrast, the numerical values overlap. For example, an integer value satisfies all of the codice_72, codice_73, codice_74, codice_75 and codice_66 predicates at the same time. (R5RS sec 6.2)


title: Scheme (programming language)

text: Scheme has three different types of equivalence between arbitrary objects denoted by three different "equivalence predicates", relational operators for testing equality, codice_77, codice_78 and codice_79:


title: Scheme (programming language)

text: Type dependent equivalence operations also exist in Scheme: codice_87 and codice_88 compare two strings (the latter performs a case-independent comparison); codice_89 and codice_90 compare characters; codice_91 compares numbers.


title: Scheme (programming language)

text: Up to the R5RS standard, the standard comment in Scheme was a semicolon, which makes the rest of the line invisible to Scheme. Numerous implementations have supported alternative conventions permitting comments to extend for more than a single line, and the R6RS standard permits two of them: an entire s-expression may be turned into a comment (or "commented out") by preceding it with codice_92 (introduced in SRFI 62) and a multiline comment or "block comment" may be produced by surrounding text with codice_93 and codice_94.


title: Scheme (programming language)

text: Scheme's input and output is based on the "port" datatype. (R5RS sec 6.6) R5RS defines two default ports, accessible with the procedures codice_95 and codice_96, which correspond to the Unix notions of standard input and standard output. Most implementations also provide codice_97. Redirection of input and standard output is supported in the standard, by standard procedures such as codice_98 and codice_99. Most implementations provide string ports with similar redirection capabilities, enabling many normal input-output operations to be performed on string buffers instead of files, using procedures described in SRFI 6. The R6RS standard specifies much more sophisticated and capable port procedures and many new types of port.


title: Scheme (programming language)

text: Similar procedures are provided for input. R5RS Scheme provides the predicates codice_100 and codice_101. For character input and output, codice_102, codice_103, codice_104 and codice_105 are provided. For writing and reading Scheme expressions, Scheme provides codice_106 and codice_107. On a read operation, the result returned is the end-of-file object if the input port has reached the end of the file, and this can be tested using the predicate codice_108.


title: Scheme (programming language)

text: In addition to the standard, SRFI 28 defines a basic formatting procedure resembling Common Lisp's codice_109 function, after which it is named.


title: Scheme (programming language)

text: In Scheme, procedures are bound to variables. At R5RS the language standard formally mandated that programs may change the variable bindings of built-in procedures, effectively redefining them. (R5RS "Language changes") For example, one may extend codice_110 to accept strings as well as numbers by redefining it:


title: Scheme (programming language)

text: In R6RS every binding, including the standard ones, belongs to some library, and all exported bindings are immutable. (R6RS sec 7.1) Because of this, redefinition of standard procedures by mutation is forbidden. Instead, it is possible to import a different procedure under the name of a standard one, which in effect is similar to redefinition.


title: Scheme (programming language)

text: In Standard Scheme, procedures that convert from one datatype to another contain the character string "->" in their name, predicates end with a "?", and procedures that change the value of already-allocated data end with a "!". These conventions are often followed by Scheme programmers.


title: Scheme (programming language)

text: In formal contexts such as Scheme standards, the word "procedure" is used in preference to "function" to refer to a lambda expression or primitive procedure. In normal usage, the words "procedure" and "function" are used interchangeably. Procedure application is sometimes referred to formally as "combination".


title: Scheme (programming language)

text: As in other Lisps, the term "thunk" is used in Scheme to refer to a procedure with no arguments. The term "proper tail recursion" refers to the property of all Scheme implementations, that they perform tail-call optimization so as to support an indefinite number of active tail calls.


title: Scheme (programming language)

text: The form of the titles of the standards documents since R3RS, "Revised Report on the Algorithmic Language Scheme", is a reference to the title of the ALGOL 60 standard document, "Revised Report on the Algorithmic Language Algol 60," The Summary page of R3RS is closely modeled on the Summary page of the ALGOL 60 Report.


title: Scheme (programming language)

text: The language is formally defined in the standards R5RS (1998) and R6RS (2007). They describe standard "forms": keywords and accompanying syntax, which provide the control structure of the language, and standard procedures which perform common tasks.


title: Scheme (programming language)

text: This table describes the standard forms in Scheme. Some forms appear in more than one row because they cannot easily be classified into a single function in the language.


title: Scheme (programming language)

text: Forms marked "L" in this table are classed as derived "library" forms in the standard and are often implemented as macros using more fundamental forms in practice, making the task of implementation much easier than in other languages.


title: Scheme (programming language)

text: Note that codice_111 is defined as a library syntax in R5RS, but the expander needs to know about it to achieve the splicing functionality. In R6RS it is no longer a library syntax.


title: Scheme (programming language)

text: The following two tables describe the standard procedures in R5RS Scheme. R6RS is far more extensive and a summary of this type would not be practical.


title: Scheme (programming language)

text: Some procedures appear in more than one row because they cannot easily be classified into a single function in the language.


title: Scheme (programming language)

text: String and character procedures that contain "-ci" in their names perform case-independent comparisons between their arguments: upper case and lower case versions of the same character are taken to be equal.


title: Scheme (programming language)

text: Because of Scheme's minimalism, many common procedures and syntactic forms are not defined by the standard. In order to keep the core language small but facilitate standardization of extensions, the Scheme community has a "Scheme Request for Implementation" (SRFI) process by which extension libraries are defined through careful discussion of extension proposals. This promotes code portability. Many of the SRFIs are supported by all or most Scheme implementations.


title: Scheme (programming language)

text: The elegant, minimalist design has made Scheme a popular target for language designers, hobbyists, and educators, and because of its small size, that of a typical interpreter, it is also a popular choice for embedded systems and scripting. This has resulted in scores of implementations, most of which differ from each other so much that porting programs from one implementation to another is quite difficult, and the small size of the standard language means that writing a useful program of any great complexity in standard, portable Scheme is almost impossible. The R6RS standard specifies a much broader language, in an attempt to broaden its appeal to programmers.


title: Scheme (programming language)

text: Almost all implementations provide a traditional Lisp-style read–eval–print loop for development and debugging. Many also compile Scheme programs to executable binary. Support for embedding Scheme code in programs written in other languages is also common, as the relative simplicity of Scheme implementations makes it a popular choice for adding scripting capabilities to larger systems developed in languages such as C. The Gambit, Chicken, and Bigloo Scheme interpreters compile Scheme to C, which makes embedding particularly easy. In addition, Bigloo's compiler can be configured to generate JVM bytecode, and it also features an experimental bytecode generator for .NET.


title: Scheme (programming language)

text: Some implementations support additional features. For example, Kawa and JScheme provide integration with Java classes, and the Scheme to C compilers often make it easy to use external libraries written in C, up to allowing the embedding of actual C code in the Scheme source. Another example is Pvts, which offers a set of visual tools for supporting the learning of Scheme.


title: Scheme (programming language)

text: Scheme is widely used by a number of schools; in particular, a number of introductory Computer Science courses use Scheme in conjunction with the textbook "Structure and Interpretation of Computer Programs" (SICP). For the past 12 years, PLT has run the ProgramByDesign (formerly TeachScheme!) project, which has exposed close to 600 high school teachers and thousands of high school students to rudimentary Scheme programming. MIT's old introductory programming class 6.001 was taught in Scheme, Although 6.001 has been replaced by more modern courses, SICP continues to be taught at MIT. Likewise, the introductory class at UC Berkeley, CS 61A, was until 2011 taught entirely in Scheme, save minor diversions into Logo to demonstrate dynamic scope. Today, like MIT, Berkeley has replaced the syllabus with a more modern version that is primarily taught in Python 3, but the current syllabus is still based on the old curriculum, and parts of the class are still taught in Scheme.