Object equality

Davy_B · September 9, 2010, 10:33am

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.TestClass.@new(5);
dynamic test2 = ruby.TestClass.@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?

Davy_B · September 9, 2010, 12:21pm

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 G.
http://hotgazpacho.org/

Davy_B · September 9, 2010, 12:53pm

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

Davy_B · September 9, 2010, 1:10pm

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 G.
http://hotgazpacho.org/

On Sep 9, 2010, at 6:52 AM, Davy B. [email protected] 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

Davy_B · September 9, 2010, 1:46pm

On Thu, Sep 9, 2010 at 1:44 PM, Davy B. [email protected] wrote:

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

Davy_B · September 9, 2010, 1:44pm

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

Davy_B · September 10, 2010, 7:10am

If any of the operands of == or != are typed to dynamic C# emits a call
to dynamic site with the corresponding operation. If the left hand side
is a Ruby object then this dynamic operation is translated to a Ruby
method call â€œ==â€ or â€œ!=â€, respectively.
The latest version of IronRuby (built from github sources) is compatible
with MRI 1.9.2 in the way â€œ!=â€ method is implemented: BasicObject#!=
calls == and negates the result. You can also provide your own
implementation of != method if its behavior should be different. This
semantics is compatible with DLR dynamic operations and everything works
as expected:

dynamic equatable = Engine.Execute(@"
class RubyEquatable
def initialize val
@val = val
end

def ==(other)
  @val == other
end

end

RubyEquatable.new(100)
");

Assert((bool)( equatable == 100));
Assert(!(bool)( equatable == 101));
Assert(!(bool)( equatable != 100));
Assert((bool)( equatable != 100));

Tomas

From: [email protected]
[mailto:[email protected]] On Behalf Of Davy B.
Sent: Thursday, September 09, 2010 4:46 AM
To: [email protected]
Subject: Re: [Ironruby-core] object equality

On Thu, Sep 9, 2010 at 1:44 PM, Davy B.
<[email protected]mailto:[email protected]> 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
<[email protected]mailto:[email protected]> 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 G.
http://hotgazpacho.org/

On Sep 9, 2010, at 6:52 AM, Davy B.
<[email protected]mailto:[email protected]> 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
<[email protected]mailto:[email protected]> 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 G.
http://hotgazpacho.org/

On Sep 9, 2010, at 4:33 AM, Davy B.
<[email protected]mailto:[email protected]> wrote:

end
p test1 == test2

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
[email protected]mailto:[email protected]
http://rubyforge.org/mailman/listinfo/ironruby-core

Ironruby-core mailing list
[email protected]mailto:[email protected]
http://rubyforge.org/mailman/listinfo/ironruby-core

Davy_B · September 10, 2010, 9:49am

great to hear, and already looking forward to the next release

just wondering though, you mentioned that it’s possible to provide your
own
implementation of !=. how would one do that? if i try to define a !=
method, i get an ‘unexpected !=’ error

On Fri, Sep 10, 2010 at 7:09 AM, Tomas M. <

Davy_B · September 10, 2010, 7:11am

There is indeed a typoâ€¦ the last line should read:
Assert((bool)( equatable != 101));

Tomas

From: Tomas M.
Sent: Thursday, September 09, 2010 10:10 PM
To: [email protected]
Subject: RE: [Ironruby-core] object equality

If any of the operands of == or != are typed to dynamic C# emits a call
to dynamic site with the corresponding operation. If the left hand side
is a Ruby object then this dynamic operation is translated to a Ruby
method call â€œ==â€ or â€œ!=â€, respectively.
The latest version of IronRuby (built from github sources) is compatible
with MRI 1.9.2 in the way â€œ!=â€ method is implemented: BasicObject#!=
calls == and negates the result. You can also provide your own
implementation of != method if its behavior should be different. This
semantics is compatible with DLR dynamic operations and everything works
as expected:

dynamic equatable = Engine.Execute(@"
class RubyEquatable
def initialize val
@val = val
end

def ==(other)
  @val == other
end

end

RubyEquatable.new(100)
");

Assert((bool)( equatable == 100));
Assert(!(bool)( equatable == 101));
Assert(!(bool)( equatable != 100));
Assert((bool)( equatable != 100));

Tomas

From: [email protected]
[mailto:[email protected]] On Behalf Of Davy B.
Sent: Thursday, September 09, 2010 4:46 AM
To: [email protected]
Subject: Re: [Ironruby-core] object equality

On Thu, Sep 9, 2010 at 1:44 PM, Davy B.
<[email protected]mailto:[email protected]> 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
<[email protected]mailto:[email protected]> 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 G.
http://hotgazpacho.org/

On Sep 9, 2010, at 6:52 AM, Davy B.
<[email protected]mailto:[email protected]> 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
<[email protected]mailto:[email protected]> 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 G.
http://hotgazpacho.org/

On Sep 9, 2010, at 4:33 AM, Davy B.
<[email protected]mailto:[email protected]> wrote:

end
p test1 == test2

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
[email protected]mailto:[email protected]
http://rubyforge.org/mailman/listinfo/ironruby-core

Ironruby-core mailing list
[email protected]mailto:[email protected]
http://rubyforge.org/mailman/listinfo/ironruby-core

Davy_B · September 10, 2010, 6:43pm

You need MRI 1.9.* or IronRuby built from github sources.
Then this just works

def !=(other)
end

Tomas

From: [email protected]
[mailto:[email protected]] On Behalf Of Davy B.
Sent: Friday, September 10, 2010 12:46 AM
To: [email protected]
Subject: Re: [Ironruby-core] object equality

great to hear, and already looking forward to the next release

just wondering though, you mentioned that it’s possible to provide your
own implementation of !=. how would one do that? if i try to define a
!= method, i get an ‘unexpected !=’ error
On Fri, Sep 10, 2010 at 7:09 AM, Tomas M.
<[email protected]mailto:[email protected]>
wrote:
If any of the operands of == or != are typed to dynamic C# emits a call
to dynamic site with the corresponding operation. If the left hand side
is a Ruby object then this dynamic operation is translated to a Ruby
method call â€œ==â€ or â€œ!=â€, respectively.
The latest version of IronRuby (built from github sources) is compatible
with MRI 1.9.2 in the way â€œ!=â€ method is implemented: BasicObject#!=
calls == and negates the result. You can also provide your own
implementation of != method if its behavior should be different. This
semantics is compatible with DLR dynamic operations and everything works
as expected:

dynamic equatable = Engine.Execute(@"
class RubyEquatable
def initialize val
@val = val
end

def ==(other)
  @val == other
end

end

RubyEquatable.new(100)
");

Assert((bool)( equatable == 100));
Assert(!(bool)( equatable == 101));
Assert(!(bool)( equatable != 100));
Assert((bool)( equatable != 100));

Tomas

From:
[email protected]mailto:[email protected]
[mailto:[email protected]mailto:[email protected]]
On Behalf Of Davy B.
Sent: Thursday, September 09, 2010 4:46 AM
To: [email protected]mailto:[email protected]
Subject: Re: [Ironruby-core] object equality

On Thu, Sep 9, 2010 at 1:44 PM, Davy B.
<[email protected]mailto:[email protected]> 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
<[email protected]mailto:[email protected]> 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 G.
http://hotgazpacho.org/

On Sep 9, 2010, at 6:52 AM, Davy B.
<[email protected]mailto:[email protected]> 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
<[email protected]mailto:[email protected]> 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 G.
http://hotgazpacho.org/

On Sep 9, 2010, at 4:33 AM, Davy B.
<[email protected]mailto:[email protected]> wrote:

end
p test1 == test2

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
[email protected]mailto:[email protected]
http://rubyforge.org/mailman/listinfo/ironruby-core

Ironruby-core mailing list
[email protected]mailto:[email protected]
http://rubyforge.org/mailman/listinfo/ironruby-core