Create a function by "hand"

This constructs a new function given it's three components: list of arguments, body code and parent environment.

Usage

function_new(args, body, env = parent.frame())

Arguments

args

A named list of default arguments. Note that if you want arguments that don't have defaults, you'll need to use the special function alist, e.g. alist(a = , b = 1)

body

A language object representing the code inside the function. Usually this will be most easily generated with quote

env

The parent environment of the function, defaults to the calling environment of make_function

Examples

f <- function(x) x + 3
g <- function_new(alist(x = ), quote(x + 3))

# The components of the functions are identical
identical(formals(f), formals(g))
#> [1] TRUE
identical(body(f), body(g))
#> [1] TRUE
identical(environment(f), environment(g))
#> [1] TRUE

# But the functions are not identical because f has src code reference
identical(f, g)
#> [1] TRUE

attr(f, "srcref") <- NULL
# Now they are:
stopifnot(identical(f, g))