From: Robert Klemme <shortcutter@...>
Date: 2011-01-12T01:20:43+09:00
Subject: Re: Best way for Array#find+transform ?

On Tue, Jan 11, 2011 at 5:02 PM, botp <botpena@gmail.com> wrote:
> On Tue, Jan 11, 2011 at 2:49 PM, David J. Hamilton <groups@hjdivad.com> wrote:
>> ...wanted to avoid having to write the transformation twice.  See his previous
>> example earlier in this thread where he uses find to get the value, and then has
>> to transform (again) the result.
>
> ah, ok (slaps my dummy head after whole thread :-)
>
> in that case, i'd still prefer something like
>
>  paths.map{|path| File.join(path,filename)}.find{|path| File.exists?(path)}
>  #=> "/opt/jruby"

Nothing built in but one could do

MapEnum = Struct.new :enum, :args, :map do
  include Enumerable

  def each
    enum.send(*args) do |*x|
      yield map[*x]
    end
  end
end

class Object
  def map_enum_for(*a, &conv)
    MapEnum.new(self, a, conv)
  end
end

filename = "ls"

p ["/usr", "/usr/local", "/opt", "/usr/bin"].map_enum_for(:each) {|x|
File.join(x,filename)}.find {|x| File.exist? x}

Cheers

robert

-- 
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/