From: Bruce Woodward <bruce.woodward@...>
Date: 2006-04-13T21:00:57+09:00
Subject: Re: map_if, collect_if ???

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Ara,

Thanks for your reply. I have been using inject but shyed away in this case
because for the 'real' code that I have been working on I am actually
already using an accumualtor.

So I had;

acc =3D []
array.each { |v|
  condition_expression and acc << v.attribute
}

Using inject seems to be roughly equivalent. In the example above v is a
instance of the Struct class.

cheers,
Bruce.

On 4/12/06, ara.t.howard@noaa.gov <ara.t.howard@noaa.gov> wrote:
>
> On Thu, 13 Apr 2006, Bruce Woodward wrote:
>
> > a =3D [ 1,2,3,4,5 ]
> >
> > b =3D a.map_if { |i|
> >  (i % 2 !=3D 0) and (i * 10)
> > }
> >
> > p b ##  [10, 30, 50]
>
> inject is very powerfull:
>
>    harp:~ > cat a.rb
>    a =3D 1 .. 5
>    b =3D a.inject([]){|a,i| i[0] =3D=3D 1 ? a.push(i * 10) : a}
>    p b
>
>    harp:~ > ruby a.rb
>    [10, 30, 50]
>
> regards.
>
> -a
> --
> be kind whenever possible... it is always possible.
> - h.h. the 14th dali lama
>
>

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