Aim: retrieving formal arguments of a function
If the function of is not a primitive, use formalArgs:
formalArgs(ls)
[1] “name” “pos” “envir” “all.names” “pattern” “sorted”
But formalArgs will return NULL if the function is a primitive (primitives don’t have formals):
formalArgs(abs) NULL —
Check if the function is a primitive:
is.primitive(abs)
[1] TRUE
If the function is a primitive, use args, and pass the output of args to formals or formalArgs:
args(abs)
function (x)
NULL
formalArgs(args(abs))
[1] “x”
formalArgs(args()) works for both primitives and non primitives:
formalArgs(args(“ls”))