Offhand I would guess it's because arrays can hold arbitrary objects.
If one array held four different classes of objects, and another held yet another four classes of objects, that's potentially sixteen spaceship operators that would need to be defined for this to make sense. And most of those would not make sense anyway.
> ara.t.how...@noaa.gov wrote: >> why __wouldn't__ one want this? >> harp:~ > cat a.rb >> a = 0,1,2 >> b = 2,3,4 >> p a < b rescue puts "can't do that!" >> class Array; include Comparable; end >> p a < b >> harp:~ > ruby a.rb >> can't do that! >> true >> ??
> Offhand I would guess it's because arrays can > hold arbitrary objects.
> If one array held four different classes of > objects, and another held yet another four > classes of objects, that's potentially sixteen > spaceship operators that would need to be > defined for this to make sense. And most of > those would not make sense anyway.
But spaceship is already defined for array (and it does the right thing (tm)). If Array is going to make spaceship available, why _not_ include Comparable?
> But spaceship is already defined for array (and it does the right > thing (tm)). If Array is going to make spaceship available, why > _not_ include Comparable?
I have to agree. I know I've wanted it a couple of times now.
On Wed, 9 Aug 2006, Hal Fulton wrote: > Offhand I would guess it's because arrays can > hold arbitrary objects.
> If one array held four different classes of > objects, and another held yet another four > classes of objects, that's potentially sixteen > spaceship operators that would need to be > defined for this to make sense. And most of > those would not make sense anyway.
i don't understand - it's up to to the objects inside the container to impliment the right methods and array already knows how to handle it:
harp:~ > cat a.rb a = 0, 'foo', 42 b = 1, 'bar', 42.0
p a < b rescue puts "can't do that"
class Array; include Comparable; end
p a < b
p a.sort_by{ rand } < b.sort_by{ rand }
harp:~ > ruby a.rb can't do that true a.rb:9:in `<': comparison of Array with Array failed (ArgumentError) from a.rb:9
if you're collections impliment <=> correctly then Array does the right thing - looping over each of them.
-a -- to foster inner awareness, introspection, and reasoning is more efficient than meditation and prayer. - h.h. the 14th dali lama
On Wed, 9 Aug 2006, Logan Capaldo wrote: > But spaceship is already defined for array (and it does the right thing > (tm)). If Array is going to make spaceship available, why _not_ include > Comparable?
yeah - exactly. by implimenting <=> it __is__ comparable in that one can indeed to
a = 0,1,2 b = 2,3,4
lt = (a <=> b) == -1 eq = (a <=> b) == 0 gt = (a <=> b) == 1
so it's just anoying that i can't acutally say
lt = a < b
2 cts.
-a -- to foster inner awareness, introspection, and reasoning is more efficient than meditation and prayer. - h.h. the 14th dali lama
ara.t.how...@noaa.gov wrote: > On Wed, 9 Aug 2006, Hal Fulton wrote:
>> Offhand I would guess it's because arrays can >> hold arbitrary objects.
>> If one array held four different classes of >> objects, and another held yet another four >> classes of objects, that's potentially sixteen >> spaceship operators that would need to be >> defined for this to make sense. And most of >> those would not make sense anyway.
> i don't understand - it's up to to the objects inside the container to > impliment the right methods and array already knows how to handle it:
> harp:~ > cat a.rb > a = 0, 'foo', 42 > b = 1, 'bar', 42.0
> p a < b rescue puts "can't do that"
> class Array; include Comparable; end
> p a < b
> p a.sort_by{ rand } < b.sort_by{ rand }
> harp:~ > ruby a.rb > can't do that > true > a.rb:9:in `<': comparison of Array with Array failed (ArgumentError) > from a.rb:9
> if you're collections impliment <=> correctly then Array does the right > thing - > looping over each of them.
> -a
FWIW, I modified the Array class to include Comparable and then ran both the test_array.rb file that's distributed with the Ruby distro and my own tests in the ruby_test project and all tests still passed.
Regards,
Dan
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