| formals {base} | R Documentation |
Access to and Manipulation of the Formal Arguments
Description
Get or set the formal arguments of a function.
Usage
formals(fun = sys.function(sys.parent()))
formals(fun, envir = environment(fun)) <- value
Arguments
fun |
a function object, or see ‘Details’. |
envir |
environment in which the function should be defined. |
value |
a list (or pairlist) of R expressions. |
Details
For the first form, fun can also be a character string
naming the function to be manipulated, which is searched for from the
parent environment.
If it is not specified, the function calling formals is used.
Only closures have formals, not primitive functions.
Value
formals returns the formal argument list of the function
specified, as a pairlist, or NULL for a
non-function or primitive.
The replacement form sets the formals of a function to the list/pairlist on the right hand side, and (potentially) resets the environment of the function.
See Also
args for a human-readable version,
alist,
body,
function.
Examples
require(stats); require(graphics)
length(formals(lm)) # the number of formal arguments
names(formals(boxplot)) # formal arguments names
f <- function(x) a+b
formals(f) <- alist(a=,b=3) # function(a,b=3)a+b
f(2) # result = 5