On Thu, Sep 9, 2010 at 1:44 PM, Davy Brion <ral...@davybrion.com> wrote:
> by default, == does a reference check in C#, unless you override it to do a > value based check (which you typically implement in Equals) > > in C#, if you want == and != to work properly you need to implement them > both. In ruby, you obviously can't implement !=, but i had (naievely > perhaps) expected that IronRuby would preserve the Ruby behavior when > calling == on an object which implements it. I _think_ that would be the > best way to handle this, though there might be very valid reasons as to why > this isn't the case at the moment. > > defining an Equals method on the ruby class which delegates to == works, > but it is somewhat weird since most people use the == and != operators to > check for equality. > > perhaps i'm better off getting rid of the == implementation and solely > providing an Equals implementation > > though the downside of that is that the ruby class doesn't stick to ruby's idioms when it comes to equality checks, which hurts its usage from other ruby code :s > > On Thu, Sep 9, 2010 at 1:10 PM, William Green <w...@hotgazpacho.org>wrote: > >> Then it would appear that in C#, using the != operator on two instances of >> Ruby objects does not call the == method on the first Ruby object and invert >> the result. >> >> Can you switch to using equals as a work-around? >> >> Not sure of the semantics around == vs .Equals in C#, but I know there is >> a semantic difference between == and eql? in Ruby. >> >> -- >> Will Green >> http://hotgazpacho.org/ >> >> >> >> On Sep 9, 2010, at 6:52 AM, Davy Brion <ral...@davybrion.com> wrote: >> >> the problem isn't with checking wether 2 objects are equal (though you >> indeed need to define an Equals method on your ruby object if you want the >> comparison to work with a direct call to .Equals... doing == in C# >> definitely uses the == method of your ruby object) but it is with the != >> check. In ruby, using != calls == and inverts the result of that. Doing != >> in C# on a ruby object doesn't seem to do the same thing. >> >> I'm also not entirely sure how it _should_ be... but as far as i can tell, >> right now, i can't get equality checks working properly with ruby objects. >> >> if a == b is true, then a != b should always be false >> if a.Equals(b) is true, then !a.Equals(b) should always be false >> >> if there's another way to get this behavior working in C# for ruby >> objects, i'd love to hear about it since it's pretty important for something >> i'm trying to do :) >> >> On Thu, Sep 9, 2010 at 12:20 PM, William Green < <w...@hotgazpacho.org> >> w...@hotgazpacho.org> wrote: >> >>> Testing for object equality in C# is different than it is in Ruby. In >>> C#, you need to override both Object.Equals and Object.GetHashCode (I >>> forget which is used when, but I do recall that the compiler complains >>> if you override one and not the other). So, when you bring your Ruby >>> object into C# and compare them, C# doesn't see an override for Equals >>> on your object, and thus uses Object.Equals (which is often what you >>> don't want). Try defining an equals method on your Ruby object, or >>> alias it to ==. >>> >>> I suspect that the == method on your Ruby object does not map to >>> Equals when you bring into C#. And I'm not sure that it should. >>> >>> Thoughts? >>> >>> -- >>> Will Green >>> <http://hotgazpacho.org/>http://hotgazpacho.org/ >>> >>> >>> >>> On Sep 9, 2010, at 4:33 AM, Davy Brion < <ral...@davybrion.com> >>> ral...@davybrion.com> wrote: >>> >>> > If i have the following class in ruby: >>> > >>> > class TestClass >>> > def initialize(value) >>> > @value = value >>> > end >>> > >>> > def ==(other) >>> > return false if other.nil? >>> > self.value == other.value >>> > end >>> > >>> > protected >>> > >>> > def value >>> > @value >>> > end >>> > end >>> > >>> > test1 = TestClass.new(5) >>> > test2 = TestClass.new(5) >>> > p test1 == test2 >>> > p test1 != test2 >>> > >>> > the output is: >>> > true >>> > false >>> > >>> > if i do this in .NET: >>> > >>> > dynamic test1 = ruby.testcla...@new(5); >>> > dynamic test2 = ruby.testcla...@new(5); >>> > >>> > var equals = test1 == test2; >>> > var differs = test1 != test2; >>> > >>> > both equals and differs are true >>> > >>> > i'm going to create an issue about this, but i do need to get this >>> working... is there a temporary workaround that i can use for now? >>> > _______________________________________________ >>> > Ironruby-core mailing list >>> > <Ironruby-core@rubyforge.org>Ironruby-core@rubyforge.org >>> > <http://rubyforge.org/mailman/listinfo/ironruby-core> >>> http://rubyforge.org/mailman/listinfo/ironruby-core >>> _______________________________________________ >>> Ironruby-core mailing list >>> <Ironruby-core@rubyforge.org>Ironruby-core@rubyforge.org >>> <http://rubyforge.org/mailman/listinfo/ironruby-core> >>> http://rubyforge.org/mailman/listinfo/ironruby-core >>> >> >> _______________________________________________ >> Ironruby-core mailing list >> Ironruby-core@rubyforge.org >> http://rubyforge.org/mailman/listinfo/ironruby-core >> >> >> _______________________________________________ >> Ironruby-core mailing list >> Ironruby-core@rubyforge.org >> http://rubyforge.org/mailman/listinfo/ironruby-core >> >> >
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