Function Methods

Every method on the built-in function type, with its signature, what it returns, and the cases where it does something other than the obvious thing.

name()

name() -> string

The function’s declared name. An anonymous function is named @anon followed by a number, counted in the order the compiler met it; a bound method reports the method’s own name, not its class’s.

%> def named(a, b, ...c) {}
%> named.name()
'named'
%> print.name()
'print'

Returns string

arity()

arity() -> number

How many parameters the function declares, counting a variadic one as a single parameter.

%> def named(a, b, ...c) {}
%> named.arity()
3

A method read off an instance counts the instance as its first parameter, so a method declaring two parameters reports 3. A foreign function from ffi has no receiver and reports its C parameter list.

Returns number

is_variadic()

is_variadic() -> bool

Whether the last parameter is variadic (...name).

%> def named(a, b, ...c) {}
%> named.is_variadic()
true

Returns bool

call()

call(...args: list) -> any

Calls the function with the given arguments and returns its result. The same as calling it directly; useful when the function is held in a variable and the call site reads better spelled out.

%> def add(a, b) { return a + b }
%> add.call(2, 3)
5

Parameters

• args (...any) — The arguments to call with.

Returns any — Whatever the function returns.

Raises anything the called function raises.

apply()

apply(args: list) -> any

Calls the function with the arguments in a list, and returns its result. call() takes them written out; this one takes them in a list.

%> def add(a, b) { return a + b }
%> add.apply([2, 3])
5
%> def collect(first, ...rest) { return [first, rest] }
%> collect.apply([1, 2, 3])
[1, [2, 3]]

A list shorter than the function’s arity leaves the remaining parameters nil, exactly as calling it directly with too few arguments does; a longer one overflows into a variadic parameter, or is discarded when there is none.

Parameters

• args (list) — The arguments to call with, in order.

Returns any — Whatever the function returns.

Raises TypeError when args is not a list, and anything the called function raises.

to_string()

to_string() -> string

The function rendered for display, as <function NAME(ARITY)>, with a trailing ... on the arity when the function is variadic.

%> def named(a, b, ...c) {}
%> named.to_string()
'<function named(3...)>'

Returns string