Issue #21821 has been updated by Eregon (Benoit Daloze). BTW `#num_waiting` is always tricky to implement so if we add new classes I would like to not have that, because it's always messy to implement and makes it e.g. impossible to reuse JDK classes for JRuby & TruffleRuby. ---------------------------------------- Feature #21821: Add Stack and SizedStack classes https://bugs.ruby-lang.org/issues/21821#change-116069 * Author: byroot (Jean Boussier) * Status: Open * Target version: 4.1 ---------------------------------------- ### Context `Queue` and `SizedQueue` are very useful and performant constructs, however they only allow for FIFO queues. Some use cases do call for LIFO queues AKA stacks. For instance, in the case of connection pool, it's often preferable to use a stack. ### Feature I'd like to introduce `Stack` and `SizedStack` classes, to mirror `Queue` and `SizedQueue`. They'd have exactly the same method and behavior at the exception of dequeuing order. ### Thread namespace? Currently `Queue` and `SizedQueue` are technically defined under `Thread` and aliased in `Object`. I wonder if that's something we should do for `Stack` too, or just some historical thing we shouldn't perpetuate. -- https://bugs.ruby-lang.org/