Issue #10984 has been updated by Cyril Vechera. I second Ilya's opinion regarding partially ordered sets. But propose to implement the comparision similiar to classes - Hash and Class both satisfies reflexive, antisymmetric, and transitive relations. So like the Class, Hash can implement <=>, returning nil on noncomparable argument. Take a look on classes: <pre> class A; end class B; end class BB < B; end </pre> How they are comparing: <pre> > A < B => nil > B < BB => false > BB < B => true > A <=> B => nil > B <=> BB => 1 </pre> ---------------------------------------- Bug #10984: Hash#contain? to check whether hash contains other hash https://bugs.ruby-lang.org/issues/10984#change-54993 * Author: Olivier Lacan * Status: Closed * Priority: Normal * Assignee: Akira Tanaka * ruby -v: * Backport: ---------------------------------------- Comparing hashes seems like a common practice but there currently isn't a method to ask a hash instance whether it includes another hash instance. The most intuitive method to reach for would be `Hash#include?` but it is in fact an alias to `Hash#has_key?` What I'm looking for can be achieved with: ~~~ class Hash def contain?(other) self.merge(other) == self end end ~~~ Here's a simple demo of `#contain?` in use: ~~~ { a: true, b: false }.contain?({ a: true}) # => true { a: true, b: false }.contain?({ b: false}) # => true { a: true, b: false }.contain?({ a: false}) # => false { a: true, b: false }.contain?({ c: true}) # => false ~~~ One important note is that this method is *not checking for nested hash matches*. This may need to be addressed when the parameters include a nested hash perhaps. Thanks to Terence Lee's help, nobu created a patch for this feature last year. I've only modified the name of the method from [his original patch](https://gist.github.com/nobu/dfe8ba14a48fc949f2ed) and attached it to this issue. ---Files-------------------------------- Hash#contain_.patch (2.22 KB) -- https://bugs.ruby-lang.org/