From: matt@... (matt neuburg)
Date: 2007-08-25T03:50:04+09:00
Subject: Re: Selecting indices from an array

William James <w_a_x_man@yahoo.com> wrote:

> On Aug 23, 8:08 am, "Ronald Fischer" <ronald.fisc...@venyon.com>
> wrote:
> > > If this is a
> > > problem, you can use this:
> >
> > > a.enum_for(:each_with_index).inject([]){|res, i|
> > >   i[0].match( /g$/) ? res << i[1] : res
> > > }
> >
> > This is an idea I like! Thanks a lot!
> >
> > Ronald
> > --
> > Ronald Fischer <ronald.fisc...@venyon.com>
> > Phone: +49-89-452133-162
> 
> accum = []
> a.each_with_index{|s,i| accum << i if s =~ /g$/ }

And to generalize further, let's abstract the test (it shouldn't matter
what the test is, just as it shouldn't matter what the array is):

#specific part
a=%w(Deutschlandsberg Stainz Preding Eibiswald)
test = Proc.new {|s| s=~/g$/}

#general part
result = []
a.each_with_index {|ss,ix| result << ix if test.call(ss)}

Or, even more general (because the names stop mattering):

def indices_matching_test(a)
  result = []
  a.each_with_index {|ss,ix| result << ix if yield ss}
  result
end

#and here's how to use it:
a=%w(Deutschlandsberg Stainz Preding Eibiswald)
test = Proc.new {|s| s=~/g$/}
puts indices_matching_test(a, &test)

m.

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