20.12.5 Function Types

Function types are denoted like:

(type,…)ret_type:

where type are the types of the arguments and ret_type is the type of the value returned by the function.

Optional arguments are marked with a ? after the type. For example, the type of the atoi function with declaration:

fun atoi = (string s, int b = 10) long: { … }

is (string,int?)long:.

If the function has variadic arguments, the position of the variadic argument in the function type specifier contains …. For example, the type of a printf function with declaration:

fun printf (string fmt, args…) void: { … }

is (string,…)void:.