From: dblack@...
Date: 2007-08-04T05:52:53+09:00
Subject: Re: Running multiple closures per iteration

Hi --

On Sat, 4 Aug 2007, Stefano Cobianchi wrote:

> On Aug 3, 7:38 pm, Joshua Chia <joshc...@gmail.com> wrote:
>> Is there a way to run more than one closure per iteration through a
>> collection?  For example, if I want to do the following two things, can
>> I combine them so that I only end up with one pass over the collection,
>> without doing a manual for loop?
>>
>> o = a.select {|x| x >= 0}
>> p = a.inject(0) {|s, x| s += x}
>
> btw, you don't need the += operator here:
> a.inject(0) {|s, x| s + x}
> => 6
>
>> Such a combination is useful when iterating through a collection is
>> expensive, e.g. on a large file on a slow disk.
>
> o = 0; p = []
> a.each { |x| o << x if x >= 0; p += x }
   a.each { |x| p << x if x >= 0; o += x }

:-)


David

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