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()
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