From: Joel VanderWerf <vjoel@...>
Date: 2009-01-12T12:14:15+09:00
Subject: Re: functional programming

Mike Gold wrote:
> Joel VanderWerf wrote:
>> Mike Gold wrote:
>>>   data = [[1,2,3], [4,5,6,7]]
>>> On this example alone, I think my characterization of "quite profound" 
>>> is justified.
>> Why isn't this the ruby candidate for comparison:
>>
>> mean = lambda { |ary|
>>    (ary.inject { |acc, x| acc + x })/ary.size.to_f
>> }
>> data.map(&mean) # => [2.0, 5.5]
> 
> Sure, you can solve a different problem than the one I gave.
> But the original problem remains.  We cannot, in general, modify
> 'mean'.
> 
> Do you propose to change every method in the ruby standard library
> to take just one argument--an array?  That would work.  Sounds like
> Lisp.

Sorry, I may not have followed the discussion very well.

But it seems more natural in this specific case to define mean to take 
one array argument, rather than *args, since (or so I imagine), that's 
usually how input will arrive. How often do you write code like

   x = ...
   y = ...
   z = ...
   m = mean.call( x,y,z )

as opposed to

   a = ...
   m = mean.call( a )

?

Perhaps I'm distracted by the specifics of mean and missing the general 
point...

-- 
       vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407