Forum: Ruby Re: Partial functions?

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Kroeger, Simon (ext) (Guest)
on 2006-05-18 18:55
(Received via mailing list)
> import functional
>
> def multiply(x, y):
>   return x * y
>
> multiply_by_3 = functional.partial(multiply, 3)
>
> multiply_by_3(4) #=> Will return 12


ruby:
gem install rubymurray
-----------------------------------------------------------
require 'curry'

def multiply x, y
  x * y
end

multiply_by_3 = method(:multiply).curry(Curry::HOLE, 3)
multiply_by_3.call(4) #=> Will return 12
-----------------------------------------------------------

cheers

Simon
unknown (Guest)
on 2006-05-19 18:52
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Taked about this with Peter V. some time ago (has it been a
year already?) We thought an underscore notation would be nice. May I
recommend a double underscore method:

  multiply_by_3 = method(:multiply).curry(__, 3)

Or course it would be nicer if one could just do:

  multiply_by_3 = multiply(__, 3)

But obviously that means changing Ruby itself a bit.
Jim W. (Guest)
on 2006-05-19 19:13
unknown wrote:
> Taked about this with Peter V. some time ago (has it been a
> year already?) We thought an underscore notation would be nice. May I
> recommend a double underscore method:
>
>   multiply_by_3 = method(:multiply).curry(__, 3)
>
> Or course it would be nicer if one could just do:
>
>   multiply_by_3 = multiply(__, 3)
>
> But obviously that means changing Ruby itself a bit.

def __() Curry::HOLE end
unknown (Guest)
on 2006-05-20 21:04
(Received via mailing list)
>>   multiply_by_3 = method(:multiply).curry(__, 3)
>>
>> Or course it would be nicer if one could just do:
>>
>>   multiply_by_3 = multiply(__, 3)
>>
>> But obviously that means changing Ruby itself a bit.

> def __() Curry::HOLE end

Thanks, Jim. That'll do the trcik for this first way --although it
isn't REAL currying actually but just method wrapping.

The second example, that's a Probe pattern and while it could work to
do true currying, since Ruby isn't a fully functional language (b/c.
if, case, and others are not true methods), then it's not fully
possible.

T.
Ross B. (Guest)
on 2006-05-20 22:20
(Received via mailing list)
On Sun, 2006-05-21 at 02:03 +0900, removed_email_address@domain.invalid wrote:
> Thanks, Jim. That'll do the trcik for this first way --although it
> isn't REAL currying actually but just method wrapping.

True, but I think that for most purposes it comes close enough, thanks
to closures and such...? I don't know how we might do 'actual currying'
in Ruby, without patching it's C-side implementation quite extensively
(and changing the way stuff works in the process - not good)...
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