[#51213] [ruby-trunk - Bug #7645][Open] BigDecimal#== slow when compared to true/false — "mathie (Graeme Mathieson)" <mathie@...>

11 messages 2013/01/01

[#51328] [ruby-trunk - Bug #7676][Open] Comparison of Float::NAN in array behaves unexpectedly — "simonrussell (Simon Russell)" <spam+ruby@...>

11 messages 2013/01/09

[#51347] [ruby-trunk - Bug #7679][Open] IRB history is broken — "zzak (Zachary Scott)" <zachary@...>

15 messages 2013/01/10

[#51389] [ruby-trunk - Bug #7688][Open] Error hiding with rb_rescue() on Comparable#==, #coerce and others — "Eregon (Benoit Daloze)" <redmine@...>

34 messages 2013/01/11

[#51430] [ruby-trunk - Bug #7696][Open] Lazy enumerators with state can't be rewound — "marcandre (Marc-Andre Lafortune)" <ruby-core@...>

15 messages 2013/01/14

[#51437] [ruby-trunk - Bug #7698][Open] RubyGems 2.0 has an incompatibility about installation of extension libraries — "mrkn (Kenta Murata)" <muraken@...>

21 messages 2013/01/15

[#51454] [CommonRuby - Feature #7701][Open] Non-optional (required) keyword args — "headius (Charles Nutter)" <headius@...>

31 messages 2013/01/15

[#51499] [ruby-trunk - Feature #7712][Open] Add .txt extensions to all plain-text documentation files for Windows users — "postmodern (Hal Brodigan)" <postmodern.mod3@...>

9 messages 2013/01/18

[#51619] [ruby-trunk - Feature #7738][Open] Deprecate Set#+ as an alias of Set#|, use it for symmetric difference. Introduce Hash#| for Hash#reverse_merge in Rails. — "alexeymuranov (Alexey Muranov)" <redmine@...>

11 messages 2013/01/24

[#51623] [ruby-trunk - Feature #7739][Open] Define Hash#| as Hash#reverse_merge in Rails — "alexeymuranov (Alexey Muranov)" <redmine@...>

24 messages 2013/01/24

[#51714] [CommonRuby - Feature #7747][Open] Expanded API for Binding semantics — "jballanc (Joshua Ballanco)" <jballanc@...>

19 messages 2013/01/27

[#51742] [ruby-trunk - Bug #7756][Open] clang 3.2 sees through UNINITIALIZED_VAR macro, gives warning — "drbrain (Eric Hodel)" <[email protected]>

10 messages 2013/01/29

[#51763] [ruby-trunk - Bug #7758][Open] Ruby on Windows crashes when active codepage is codepage 65001 and outputting unicode character — "joshc (Josh C)" <josh.nw@...>

16 messages 2013/01/30

[ruby-core:51620] [ruby-trunk - Feature #7738] Deprecate Set#+ as an alias of Set#|, use it for symmetric difference. Introduce Hash#| for Hash#reverse_merge in Rails.

From: "trans (Thomas Sawyer)" <transfire@...>
Date: 2013-01-24 12:20:47 UTC
List: ruby-core #51620
Issue #7738 has been updated by trans (Thomas Sawyer).


It would help if you gave some examples of what "symmetric difference" actually meant.


Put the last "I also suggest" in another issue. Ok?


----------------------------------------
Feature #7738: Deprecate Set#+ as an alias of Set#|, use it for symmetric difference.  Introduce Hash#| for Hash#reverse_merge in Rails.
https://bugs.ruby-lang.org/issues/7738#change-35579

Author: alexeymuranov (Alexey Muranov)
Status: Open
Priority: Normal
Assignee: 
Category: 
Target version: Next Major


=begin
I am almost sure this will be rejected, but i want to try anyway.  My goal is to propose a more efficient and consistent use of binary operator symbols for some classes, in this case for (({Set})) and (({Hash})).

I propose to deprecate (({Set#+})) as an alias of (({Set#|})), and use (({Set#+})) later for the ((*symmetric difference*)) of sets.  I think that operator symbols like (({+})) and (({|})) are too precious to alias one another.

Currently (({Set#+})) is probably the only use of (({#+})) for an operation which is not ((*injective*)) in each of the arguments: for sets (({a})), (({b})), (({c})), the equality

  a + b == a + c

does not currently imply

  b == c

The natural binary operation on sets that is injective in each argument is the ((*symmetric difference*)), it corresponds to the bitwise XOR.  I have also noticed that the "(({+}))" for sets is used in "Lectures on ergodic theory " by P. Halmos to denote the symmetric difference.

I also suggest for to define (({Hash#|})) as Hash#reverse_merge in Rails, in my opinion this would correspond nicely to (({Set#|})).
=end



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