From: Tomas Pospisek's Mailing Lists <tpo2@...>
Date: 2007-05-29T00:52:12+09:00
Subject: Re: Perspectives for Ruby 2.0

On Mon, 28 May 2007, Michael Hollins wrote:

> arcadiorubiogarcia@gmail.com wrote:
>> On May 27, 12:31 pm, Michael Hollins <m...@hollins.id.au> wrote:
>>> arcadiorubiogar...@gmail.com wrote:
>>> 
>>>> 1. Are there any plans to introduce function currying? It's a very
>>>> useful feature for function expressions, and it won't be very
>>>> difficult to add. In fact, far I've seen a few implementations of it
>>>> out there. They seem to be more or less ok, but it would be great to
>>>> have it on the standard distribution.
>>> what would you want beyond the following?
>>> 
>>> http://moonbase.rydia.net/mental/blog/programming/currying-in-ruby
>> 
>> Well I would want something more implicit, like in Groovy for
>> instance:
>> http://www.ibm.com/developerworks/java/library/j-pg08235/index.html
>> 
>> 
>
> So, just so I understand, take the following example:
>
>  def multiply(a,b)
>    a * b
>  end
>
>  triple = lambda { |a| multiply(a,3) }
>
>  puts triple.call(10)
>
> I believe you are saying that you'd like the last line to be:
>
>  puts triple(10)
>
> Is that right? If so, then I agree that would be nice. I'm guessing that it's 
> difficult to achieve in ruby due to the fact that functions can be called 
> without the parentheses. So, for example if I defined the following 
> uninteresting lambda:
>
>  six = lambda { multiply(2,3) }
>
> then the following would be ambiguous:
>
>  puts six
>
> Am I trying to invoke the lambda, or am I trying to print the value of the 
> object? To resolve the ambiguity I cannot invoke a lambda with the above 
> syntax. Instead I need to do:
>
>  puts six.call()
>
> I'd like to hear from the experts if that is the reason or whether there is 
> something more fundamental. I'm still learning ruby (and liking it BTW), so 
> others will likely have a clearer perspective.

The ambiguity is there allready

If I write:

    puts nuts

Then nuts can either be a variable that will return its value, or it can 
be a function call that will return the result of calling it. In that 
sense being able to call (from your example above):

   puts six

would be IMHO perfectly sensible, since it would be neither more nor less 
ambiguous then ruby's default behaveour.
*t

--
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   Tomas Pospisek
   http://sourcepole.com -  Linux & Open Source Solutions
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