npm package: @hypercubed/f-flat
Description: F♭ (pronounced F-flat) is a toy language.
Author: J. Harshbarger
Latest version: 0.0.7

# F♭

F♭ (pronounced F-flat) is a toy language.

F♭ is a dynamically typed array-oriented concatenative language like Forth, Joy, and [others](http://www.concatenative.org/). F♭ is meant to be used interactively, for example in a CLI REPL, like R or the command shell, or in a stack based calculator.  This constraint dictates many of the language features.

## Features

### Flat functional [concatenative language](http://concatenative.org/wiki/view/Front%20Page)

### Stack based

### RPN

### Dynamic Types

### Arbitrary-precision decimal and complex number type.

### JSON format is a valid f-flat programs.

## Why?

* Designing a programming language in another language is a great way to learn about programming languages in general and the host language in particular.

* Concatenative languages, with inherent functional composition, are a great way to explore functional programming and mathematics.  Higher order functions (including math functions) are composed of smaller functions.

* Because 0.1 + 0.2 = 0.3 and sqrt of -1 is not "not a number".

## Example

[![asciicast](https://asciinema.org/a/39282.png)](https://asciinema.org/a/39282)

```forth
Welcome to F♭ REPL Interpreter
F♭ Version 0.0.0 (C) 2000-2017 J. Harshbarger

f♭> 0.1 0.2 +
[ 0.3 ]

f♭> 0.3 =
[ true ]

f♭> clr
[]

f♭> -1 sqrt
[ 0+1i ]

f♭> 1 atan 4 *
[ 0+1i, 3.1415926535897932385 ]

f♭> * exp
[ -1-3.7356616720497115803e-20i ]

f♭> abs
[ 1 ]

f♭> clr
[]

f♭> [ 2 swap ^ 1 - prime? ] "mersenne?" def
[]

f♭> 10 integers
[ [ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 ] ]

f♭> [ mersenne? ] map
[ [ true, true, true, false, true, false, true, false, false, false ] ]

f♭> clr
[]

f♭> 1000 !
[ 4.0238726007709377384e+2567 ]

f♭> clr
[]

f♭> i !
[ 0.49801566811835599106-0.15494982830181068731i ]

f♭> { first: "Manfred" }
[ { first: 'Manfred' } ]

f♭> { last: 'von Thun' }
[ { first: 'Manfred' }, { last: 'von Thun' } ]

f♭> +
[ { first: 'Manfred', last: 'von Thun' } ]

f♭> clr
[  ]

f♭> [ 1 2 3 ]
[ [ 1 2 3 ] ]

f♭> dup
[ [ 1 2 3 ] [ 1 2 3 ] ]

f♭> [ 2 * ]
[ [ 1 2 3 ] [ 1 2 3 ] [ 2 * ] ]

f♭> map
[ [ 1 2 3 ] [ 2 4 6 ] ]

f♭> +
[ [ 1 2 3 2 4 6 ] ]

f♭> +
[ [ 1 2 3 2 4 6 ] ]

f♭> clr
[  ]

f♭> dbl-sqr-cat: [ dup [ 2 * ] map + ] ;
[  ]

f♭> [ 1 2 3 ]
[ [ 1 2 3 ] ]

f♭>  dbl-sqr-cat
[ [ 1 2 3 2 4 6 ] ]

f♭> 'dbl-sqr-cat' see
[ '[ dup [ 2 * ] map + ]' ]

f♭> drop
[  ]

f♭> dbl-sqr-cat: expand
[ dup,2,*,*,Symbol((),swap,eval,dequote,+ ]

```

See other examples and guides [here](./docs/).

## Project Goals

* conceptually simple
* interactive first
  * minimal hidden state
  * easy to type and read
  * reads left to right, top to bottom
  * whitespace not significant syntax
  * no lambdas/parameters
  * interactive development
  * case insensitive
* flat concatenative language
  * name code not values
  * multiple return values
  * concatenation is composition/pipeline style
  * no unnecessary parentheses
* no surprises
  * immutable data
  * arbitrary-precision decimal and complex numbers
  * percent values
  * both double and single quotes
  * returns error objects (TBD)
* pure functions
* host language interface (TBD)
* session saving (TBD)
  * undo/redo
  * state is serializable (TBD)
* modules, namespaces, and "closures"

## Influences

* [Many concatenative languages](http://concatenative.org/wiki/view/Front%20Page) (HP RPL, Forth, Joy, Factor, XY)
* Haskell
* JavaScript

## License

MIT