Access to and Manipulation of the Formal Arguments
DESCRIPTION:
Get or set the formal arguments of a function.
USAGE:
formals(fun)
formals(fun) <- value
REQUIRED ARGUMENTS:
fun
a function object.
OPTIONAL ARGUMENTS:
value
a list of expressions with named elements. The element
names will be the argument names and the values will be the default
argument values.
VALUE:
a list where element names are the argument names and their values
are the default argument values.
SIDE EFFECTS:
The assignment function sets the formal arguments of the function to the
list on the right hand side. No consistency with current argument names or
number is enforced or checked for. All existing arguments are replaced by
the new list of arguments.
DETAILS:
When calling the function
formals(), the
fun
argument
can be a character string giving the name of a function.
These functions emulate R functions of the same name, but are
somewhat different. The S-PLUS version of
formals()
does not have a default value for the
fun argument.
The S-PLUS version of
formals()<- does not
have the
envir argument that the R includes.
SEE ALSO:
,
.
EXAMPLES:
# Getting names of formal arguments
names(formals(persp))
# Setting formal arguments
func <- function(x) a + b
formals(func) <- list(a = NULL, b = 3)
func(10)