From: Mauricio Fernandez <mfp@...>
Date: 2006-01-08T03:27:07+09:00
Subject: Re: Iterator Fu Failing Me

On Sun, Jan 08, 2006 at 01:13:00AM +0900, Robert Klemme wrote:
> Bob Hutchison <hutch@recursive.ca> wrote:
> >On Jan 6, 2006, at 11:36 PM, James Edward Gray II wrote:
> >
> >>That works.  Now can anyone give me a version of the middle section
> >>that doesn't require I call parse?() 50 times?  I want something
> >>close to:
> >>
> >>  elements = tokens.map do |token|
> >>    [ClassA, ClassB, ClassC].find { |kind| kind.parse?(token) }
> >>  end
> >>
> >>Except that I want the return result of parse?(), instead of the
> >>class that took it.
> >
> >Why not:
> >
> >elements = tokens.map do |token|
> >  result = nil
> >  [ClassA, ClassB, ClassC].find { |kind| result = kind.parse?(token) }
> >end
> 
> Because this won't return the proper value from the block.  You need at 
> least to add a line with "result" after the #find. :-)  And then it's much 
> more inelegant than using #detect. :-)

Actually,

enum.c:
    rb_define_method(rb_mEnumerable,"find", enum_find, -1);
    rb_define_method(rb_mEnumerable,"detect", enum_find, -1);

...

(1..10).detect{|x| 10*x > 50}                      # => 6

...

-- 
Mauricio Fernandez