From: Robert Dober <robert.dober@...>
Date: 2006-04-13T22:24:28+09:00
Subject: Re: map_if, collect_if ???

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On 4/13/06, Kroeger, Simon (ext) <simon.kroeger.ext@siemens.com> wrote:
>
> > > module Enumerable
> > >     def map_if( &block )
> > >         find_all(&block).map(&block)
> > >     end
> > > end
> > [...]
> > I will file away the find_all  {}.map {} idiom for future use
> > [...]
>
> I would change that to:
>
>     map(&block).select{|e|e}
>
> there can be surprising side effects if the user doesn't
> expect the block to be called twice for each element.
>
> cheers
>
> Simon


Good point.
This block twice thing felt elegant and wrong in the same place.
I thaught that perfomance should not be a design issue, but Bruce's point
was well taken.
The side effect thing might not strike often, but if it strikes, boy I woul=
d
not want to debug that baby.

Nice discussion.

Robert




--
Deux choses sont infinies : l'univers et la b=EAtise humaine ; en ce qui
concerne l'univers, je n'en ai pas acquis la certitude absolue.

- Albert Einstein

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