The CRAN version of the R package wrapr package now includes a concise anonymous function constructor: l().
To use it please do the following: attach wrapr and ask it to place a definition for l() in your environment:
library("wrapr")
wrapr::defineLambda(name = "l")
ls()## [1] "X" "Y" "df" "f" "inputs" "l" "x"Note: throughout this document we are using the letter “l” as a stand-in for the Greek letter lambda, as this non-ASCII character can cause formatting problems in some situations.
You can use l() to define functions. The syntax is: l(arg [, arg]*, body [, env=env]). That is we write a l()-call (which you can do by cutting and pasting) and list the desired function arguments and then the function body. For example the function that squares numbers is:
l(x, x^2)## function (x)
## x^2We can use such a function to square the first four positive integers as follows:
sapply(1:4, l(x, x^2))## [1] 1 4 9 16Dot-pipe style notation does not need the l() factory as it treats pipe stages as expressions parameterized over the variable “.”:
1:4 %.>% { .^2 }## [1] 1 4 9 16If you do want an operator notation for function construction you can also use on of the variations of the named map builder:
(1:4) %.>% (x := { x^2 })(.)## [1] 1 4 9 16And we can build functions that take more than one argument as follows:
l(x, y, x + 3*y)## function (x, y)
## x + 3 * y