From: "zakhar (Isaac Schwabacher)" <ischwabacher@...>
Date: 2013-10-30T03:50:15+09:00
Subject: [ruby-core:58070] [ruby-trunk - Bug #9059][Open] Equal Time objects	don't hash equal


Issue #9059 has been reported by zakhar (Isaac Schwabacher).

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Bug #9059: Equal Time objects don't hash equal
https://bugs.ruby-lang.org/issues/9059

Author: zakhar (Isaac Schwabacher)
Status: Open
Priority: Normal
Assignee: 
Category: 
Target version: 
ruby -v: ruby 2.0.0p247 (2013-06-27 revision 41674) [x86_64-darwin12.4.0]
Backport: 1.9.3: UNKNOWN, 2.0.0: UNKNOWN


=begin
Time objects break the promise that if (({t0.eql? t1})), then (({t0.hash == t1.hash})).
It is possible that this is related to the resolution of ((<this problem|URL:https://www.ruby-forum.com/topic/4415234>)), since both issues seem to be related to round-off error.

 #!/usr/bin/env ruby
 
 require 'minitest/autorun'
 
 describe Object do
   before do
     t0 = Time.new(2013, 10, 29, 12, 30, 27)
     t1 = t0 + 0.1 + 0.1 + 0.1 + 0.1 + 0.1 + 0.1 + 0.1 + 0.1 + 0.1 + 0.1
     t_midnight = Time.new(2013, 10, 29)
     @x = t0 - (t0.to_r - t_midnight.to_r) % 60
     @y = t1 - (t1.to_r - t_midnight.to_r) % 60
   end
 
   it "should hash equal to eql objects" do
     if @x.respond_to? :eql? and @x.respond_to? :hash and @y.respond_to? :hash
       @x.hash.must_equal @y.hash if @x.eql? @y
     end
   end
 end

This test also failed on ruby -v ((%ruby 1.9.2p290 (2011-07-09 revision 32553) [x86_64-linux]%)).
If I had to guess, I would say that the instance variables from which (({@t0.tv_*})) and (({@t1.tv_*})) are computed are (({#==})) but not (({#eql?})), and that (({Time#eql?})) is (correctly, I think) using (({#==})) to compare these, but (({Time#hash})) is using their (({#hash}))es directly rather than converting them to a common type first.

=end



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