R: free operator language. (自由演算子言語R）

In R, you can freely define a new binary operator with the form of `%hoge%` where `hoge` is arbitral literal. This philosophy allows us to flexibly extend the original syntax; actually free operators are sometimes very useful in terms of readability/writability.

At the same time, however, this means R has a lot of duplicated operators as shown below. If you load two or more packages that export free operators, you may suffer from name conflicts and it will be hard to predict the behavior.

（Rって好きに演算子作れて、それはそれでいいんだけど、パッケージ間の名前衝突多すぎて危ないんじゃね？）

Data from http://finzi.psych.upenn.edu/R/library/ on Oct, 25, 2014.

We show only the packages on CRAN, but recent packages on github may tend more to use free operator.

（CRANのパッケージだけ載せてるけど、githubの奴も入れるともっと多いかも）

# Duplicated free operators (重複のある自由演算子)

| Ind|Op    |Package        |Description                                                                                   |
|---:|:-----|:--------------|:---------------------------------------------------------------------------------------------|
|   1|%nin% |BBmisc         |                           Simply a negated 'in' operator.                                    |
|   1|%nin% |DescTools      |                           Find Matching (or Non-Matching) Elements                           |
|   1|%nin% |Hmisc          |                  Find Matching (or Non-Matching) Elements                                    |
|   1|%nin% |memisc         |                           Negative Match                                                     |
|   2|%*%   |bigalgebra     |%*%,big.matrix,big.matrix-method                                                              |
|   2|%*%   |compositions   |                             inner product for matrices and vectors                           |
|   2|%*%   |compositions   |                       inner product for datasets with a vector space structure               |
|   2|%*%   |compositions   |                       inner product for datasets with vector scale                           |
|   2|%*%   |gmatrix        |                     Matrix Multiplication                                                    |
|   2|%*%   |HiPLARM        |                             Matrix Multiplication of two matrices using GPU or multi-core    |
|   2|%*%   |kinship        |                    Basic Linear Algebra for classes bdsmatrix and                            |
|   2|%*%   |Matrix         |            Matrix (Cross) Products (of Transpose)                                            |
|   2|%*%   |orientlib      |%*%,orientation,orientation-method                                                            |
|   2|%*%   |quaternions    |                  Linear Algebra with quaternions                                             |
|   3|%>%   |dendextend     |                             Pipe an object forward into a function call/expression.          |
|   3|%>%   |ggvis          |                             Pipe graphics                                                    |
|   3|%>%   |gmailr         |                             Pipe statements                                                  |
|   3|%>%   |magrittr       |                             Pipe an object forward into a function call/expression.          |
|   4|%+%   |DepthProc      |                             Adds plots                                                       |
|   4|%+%   |Jmisc          |                             Concatenate two strings                                          |
|   4|%+%   |lava           |                    Concatenation operator                                                    |
|   4|%+%   |stringi        |                             Concatenate Two Character Vectors                                |
|   5|%in%  |discreteRV     |                            Generic method for in operator function                           |
|   5|%in%  |flowCore       |                    Filter-specific membership methods                                        |
|   6|%s%   |matrixcalc     |                             Direct sum of two arrays                                         |
|   6|%s%   |Rgnuplot       |                             String concatenation operator                                    |
|   7|%!in% |operator.tools |                           Logical Operator: NOT IN                                           |
|   7|%!in% |operators      |                           Not in                                                             |
|   8|%~%   |operators      |                             Pattern matching operators                                       |
|   8|%~%   |reportr        |                             Test a character vector for a match against a regular expression |
|   9|%<%   |scidb          |                             Masking comparison methods from package 'scidb'                  |
|   9|%<%   |stringi        |                             Compare Strings with or without Collation                        |
|   9|%<%   |TeachingDemos  |                             Less than or Less than and equal operators that can be chained   |

# A complete list of free operators (全自由演算子の一覧）

|Op           |Package         |Description                                                                                   |
|:------------|:---------------|:---------------------------------------------------------------------------------------------|
|%same%       |BayesFactor     |                          Compare two objects to see if they are the 'same', for some loose   |
|%termin%     |BayesFactor     |                        Find a model term in a vector of                                      |
|%btwn%       |BBmisc          |                          Check if some values are covered by the range of the values in a    |
|%nin%        |BBmisc          |                           Simply a negated 'in' operator.                                    |
|%nin%        |DescTools       |                           Find Matching (or Non-Matching) Elements                           |
|%nin%        |Hmisc           |                  Find Matching (or Non-Matching) Elements                                    |
|%nin%        |memisc          |                           Negative Match                                                     |
|%inInterval% |BEQI2           |                    Test if a Value is in an Interval                                         |
|%*%          |bigalgebra      |%*%,big.matrix,big.matrix-method                                                              |
|%*%          |compositions    |                             inner product for matrices and vectors                           |
|%*%          |compositions    |                       inner product for datasets with a vector space structure               |
|%*%          |compositions    |                       inner product for datasets with vector scale                           |
|%*%          |gmatrix         |                     Matrix Multiplication                                                    |
|%*%          |HiPLARM         |                             Matrix Multiplication of two matrices using GPU or multi-core    |
|%*%          |kinship         |                    Basic Linear Algebra for classes bdsmatrix and                            |
|%*%          |Matrix          |            Matrix (Cross) Products (of Transpose)                                            |
|%*%          |orientlib       |%*%,orientation,orientation-method                                                            |
|%*%          |quaternions     |                  Linear Algebra with quaternions                                             |
|%>%          |dendextend      |                             Pipe an object forward into a function call/expression.          |
|%>%          |ggvis           |                             Pipe graphics                                                    |
|%>%          |gmailr          |                             Pipe statements                                                  |
|%>%          |magrittr        |                             Pipe an object forward into a function call/expression.          |
|%+%          |DepthProc       |                             Adds plots                                                       |
|%+%          |Jmisc           |                             Concatenate two strings                                          |
|%+%          |lava            |                    Concatenation operator                                                    |
|%+%          |stringi         |                             Concatenate Two Character Vectors                                |
|%c%          |DescTools       |                             Concatenates two strings without any separator.                  |
|%like%       |DescTools       |                          Like operator                                                       |
|%overlaps%   |DescTools       |                      Determines If And How Extensively Two Date Ranges Overlap               |
|%AND%        |discreteRV      |                           Compute the logical AND of two events                              |
|%in%         |discreteRV      |                            Generic method for in operator function                           |
|%in%         |flowCore        |                    Filter-specific membership methods                                        |
|%OR%         |discreteRV      |                            Compute the logical OR of two events                              |
|%dorng%      |doRNG           |                         Reproducible Parallel Foreach Backend                                |
|%contains%   |dostats         |                      Does a table contain a value                                            |
|%SplitOn%    |favir           |              Split a character type at the given substring                                   |
|%on%         |flowCore        |                            Methods for Function %on% in Package 'flowCore'                   |
|%must%       |futile.paradigm |                 Add post-assertion validations to a function to                              |
|%when%       |futile.paradigm |                 Add guards to a function to define the                                       |
|%._.%        |labeledLoop     |                           Labeled loop and break                                             |
|%as%         |lambda.r        |                            Define functions and type constructors in lambda.r                |
|%isa%        |lambda.r        |                           Functions for duck typing                                          |
|%ni%         |lava            |                   Matching operator (x not in y) oposed to the '%in%'-operator (x in y)      |
|%m+%         |lubridate       |                            Add and subtract months to a date without exceeding the last day  |
|%within%     |lubridate       |                        Tests whether a date or interval falls within an interval             |
|%s%          |matrixcalc      |                             Direct sum of two arrays                                         |
|%s%          |Rgnuplot        |                             String concatenation operator                                    |
|%!in%        |operator.tools  |                           Logical Operator: NOT IN                                           |
|%!in%        |operators       |                           Not in                                                             |
|%-~&#124;%   |operators       |                           Remove a pattern from a character vector                           |
|%/~%         |operators       |                            Divide by a pattern                                               |
|%+=%         |operators       |                            Plus Equal Operators                                              |
|%<<%         |operators       |                            Read or write an R object to/from a file                          |
|%&#124;%     |operators       |                             Pipe an R object to a unix command                               |
|%~%          |operators       |                             Pattern matching operators                                       |
|%~%          |reportr         |                             Test a character vector for a match against a regular expression |
|%~&#124;%    |operators       |                            Regular expression filters                                        |
|%but%        |operators       |                           Modification of function arguments                                 |
|%o~%         |operators       |                            Only keeps the macthing part of a regular expression              |
|%of%         |operators       |                            Is an object of a given class                                     |
|%without%    |operators       |                       Remove certain elements from a vector                                  |
|%x=%         |operators       |                            Creates string decorators by repeating a pattern                  |
|%k%          |opm             |                             Query metadata keys                                              |
|%q%          |opm             |                             Query metadata                                                   |
|%grep%       |osmar           |                          Binary operators for grep-like functions                            |
|%>>%         |pipeR           |                            Pipe an object forward                                            |
|%--%         |powerr          |                            Binary operator %-%                                               |
|%.*%         |powerr          |                            Binary operator %.*%                                              |
|%**%         |powerr          |                            Binary operator %**%                                              |
|%++%         |powerr          |                            Binary operator %++%                                              |
|%<a-%        |pryr            |                           Create an active binding.                                          |
|%<c-%        |pryr            |                           Create a constant (locked) binding.                                |
|%<d-%        |pryr            |                           Create an delayed binding.                                         |
|%.%          |pvar            |                             Concatenate strings                                              |
|%&%          |qdap            |                             qdap Chaining                                                    |
|%l*%         |qdapTools       |                            Hash/Dictionary Lookup                                            |
|%append%     |RecordLinkage   |       Concatenate comparison patterns or                                                     |
|%or%         |rex             |                            Or                                                                |
|%out%        |rmngb           |                           The Opposite of '%in%'                                             |
|%^%          |rmutil          |of a Matrix                                                                                   |
|%and%        |RQDA            |                           Binary operations of some types of RQDA objects                    |
|%Q-%         |RSpincalc       |                            Quaternion subtraction                                            |
|%Q.%         |RSpincalc       |                            Quaternion dot product                                            |
|%Q*%         |RSpincalc       |                            Quaternion multiplication                                         |
|%Q/%         |RSpincalc       |                            Quaternion division                                               |
|%Q+%         |RSpincalc       |                            Quaternion addition                                               |
|%<%          |scidb           |                             Masking comparison methods from package 'scidb'                  |
|%<%          |stringi         |                             Compare Strings with or without Collation                        |
|%<%          |TeachingDemos   |                             Less than or Less than and equal operators that can be chained   |
|%tt%         |STAR            |                            Time Transformation Using a gssanova Objet                        |
|%included%   |timetools       |                      test inclusion of 2 'POSIXcti' objects                                  |
|%intersect%  |timetools       |                     intersects 2 'POSIXcti' objects                                          |