From: akr@... Date: 2015-11-10T03:45:09+00:00 Subject: [ruby-core:71427] [Ruby trunk - Feature #10984] Hash#contain? to check whether hash contains other hash Issue #10984 has been updated by Akira Tanaka. Nobuyoshi Nakada wrote: > If we'll introduce `Hash#<=` and `Hash#>=`, then `Hash#<` and `Hash#>` too? Maybe. Usefulness of `Hash#<` and `Hash#>` is not discussed well, though. > `Hash` will include `Comparable` with `Hash#<=>`? No. It is clearly stated by matz. ``` % ruby -e ' class Hash def <=(other) self.merge(other) == other end def >=(other) self.merge(other) == self end def <(other) self <= other && self != other end def >(other) self >= other && self != other end end hs = [{a:1, b:2}, {a:1, b:2, c:3}] ops = %w[<= >= < >] ops.each {|op| hs.each {|h1| hs.each {|h2| puts "#{h1} #{op} #{h2} = #{h1.send(op, h2)}" } } } ' {:a=>1, :b=>2} <= {:a=>1, :b=>2} = true {:a=>1, :b=>2} <= {:a=>1, :b=>2, :c=>3} = true {:a=>1, :b=>2, :c=>3} <= {:a=>1, :b=>2} = false {:a=>1, :b=>2, :c=>3} <= {:a=>1, :b=>2, :c=>3} = true {:a=>1, :b=>2} >= {:a=>1, :b=>2} = true {:a=>1, :b=>2} >= {:a=>1, :b=>2, :c=>3} = false {:a=>1, :b=>2, :c=>3} >= {:a=>1, :b=>2} = true {:a=>1, :b=>2, :c=>3} >= {:a=>1, :b=>2, :c=>3} = true {:a=>1, :b=>2} < {:a=>1, :b=>2} = false {:a=>1, :b=>2} < {:a=>1, :b=>2, :c=>3} = true {:a=>1, :b=>2, :c=>3} < {:a=>1, :b=>2} = false {:a=>1, :b=>2, :c=>3} < {:a=>1, :b=>2, :c=>3} = false {:a=>1, :b=>2} > {:a=>1, :b=>2} = false {:a=>1, :b=>2} > {:a=>1, :b=>2, :c=>3} = false {:a=>1, :b=>2, :c=>3} > {:a=>1, :b=>2} = true {:a=>1, :b=>2, :c=>3} > {:a=>1, :b=>2, :c=>3} = false ``` ---------------------------------------- Feature #10984: Hash#contain? to check whether hash contains other hash https://bugs.ruby-lang.org/issues/10984#change-54795 * Author: Olivier Lacan * Status: Open * Priority: Normal * Assignee: Akira Tanaka ---------------------------------------- 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/