Maybe and when

williamthome · May 15, 2024, 12:13pm

There is a discussion about it here.

I started to implement it some time ago:

github.com/erlang/otp

Support guards in maybe expression

erlang:master ← williamthome:maybe-guards

opened 09:35PM - 08 Oct 23 UTC

williamthome

+62 -16

This PR implements guards in maybe expressions. The motivation for the PR is [t…his topic](https://erlangforums.com/t/support-guards-in-erlang-maybe/2406) by @josevalim in Erlang Forums. ## Example ```erlang -module(maybe_guard). -feature(maybe_expr, enable). -export([t/1]). t(X) -> maybe Zero when Zero =:= 0 ?= X, One when One > 0, One < 2 ?= one(), ok else X -> {nonzero, X} end. one() -> 1. ``` ```console 1> maybe_guard:t(0). ok 2> maybe_guard:t(1). {nonzero,1} ``` ## Notes There are things to fix, but this PR is to start the discussion for the implementation of this feature.