formals(fun = sys.function(sys.parent()))
formals(fun, envir = environment(fun)) <- valueformals 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.
For the first form, fun can also be a character string naming
the function to be manipulated, which is searched for from the parent
frame. If it is not specified, the function calling formals is
used.
Only closures have formals, not primitive functions.
args for a human-readable version,
alist,
body,
function.
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
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