Extract arguments from a function
fn_fmls() returns a named list of formal arguments.
fn_fmls_names() returns the names of the arguments.
fn_fmls_syms() returns formals as a named list of symbols. This
is especially useful for forwarding arguments in constructed calls.
fn_fmls(fn = caller_fn()) fn_fmls_names(fn = caller_fn()) fn_fmls_syms(fn = caller_fn()) fn_fmls(fn) <- value fn_fmls_names(fn) <- value
fn |
A function. It is lookep up in the calling frame if not supplied. |
value |
New formals or formals names for |
Unlike formals(), these helpers throw an error with primitive
functions instead of returning NULL.
# Extract from current call:
fn <- function(a = 1, b = 2) fn_fmls()
fn()
# fn_fmls_syms() makes it easy to forward arguments:
call2("apply", !!! fn_fmls_syms(lapply))
# You can also change the formals:
fn_fmls(fn) <- list(A = 10, B = 20)
fn()
fn_fmls_names(fn) <- c("foo", "bar")
fn()Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.