From: "trans (Thomas Sawyer)" <transfire@...> Date: 2012-11-12T23:41:43+09:00 Subject: [ruby-core:49255] [ruby-trunk - Feature #5185] Set#merge acts in place but Hash#merge does not Issue #5185 has been updated by trans (Thomas Sawyer). Well, maybe #merge wasn't the best choice for Hash in the first place. Who knows. I only know that polymorphism is so incredibly useful in OOP, that it's a chink in the armor for the language when inconsistencies of this nature remain. ---------------------------------------- Feature #5185: Set#merge acts in place but Hash#merge does not https://bugs.ruby-lang.org/issues/5185#change-32816 Author: trans (Thomas Sawyer) Status: Rejected Priority: Normal Assignee: knu (Akinori MUSHA) Category: lib Target version: 2.0.0 Waste of brain cells to have to learn and recall they are different. The expected method would be Set#merge!, Set#merge would return a new Set instance. OTOH, why not Set#concat ? Or conversely, Array#merge ? -- http://bugs.ruby-lang.org/