proto

A shared front-end for a family of multi candidates.

A proto declares the common shape of a multi family — one place to name the routine and, optionally, run shared code around every candidate. The body {*} means "dispatch to the best matching multi".

Declaring a proto #

proto describe(|) {*}
multi describe(Int $) { "int" }
multi describe(Str $) { "str" }
say describe(5);
say describe("x");

int
str

The proto's signature (|) accepts any arguments (a capture); each multi narrows it, and {*} hands off to the one that fits.

Notes #

• A proto is optional — a bare set of multis works — but it documents the family and gives the routine one signature ((|) here) that every candidate narrows.
• The proto fixes the routine's name and shared signature; individual candidates fill in the behaviour — see Multi dispatch.
• In Rakudo the {*} may be surrounded by code that runs once before dispatch (to validate or transform arguments); **Raku++ treats the proto as dispatch-only** and does not run that surrounding code, so keep such logic inside the candidates.