From: Leslie Viljoen <leslieviljoen@...>
Date: 2006-08-13T05:22:41+09:00
Subject: Re: Dire need for inject_with_index

On 8/12/06, Leslie Viljoen <leslieviljoen@gmail.com> wrote:
> On 8/12/06, James Edward Gray II <james@grayproductions.net> wrote:
> > Hope this helps:
> >
> >  >> require "enumerator"
> > => true
> >  >> module Enumerable
> >  >>   def inject_with_index(*args, &block)
> >  >>     enum_for(:each_with_index).inject(*args, &block)
> >  >>   end
> >  >> end
> > => nil
> >  >> ("A".."D").inject_with_index("") do |str, (let, i)|
> > ?>   i % 2 == 0 ? str += let : str
> >  >> end
> > => "AC"

What I don't understand about your solution is the "do |str, (let, i)|",
how can you have brackets in there? What does that do?

Your example works as above but I can't get it to work with an array.
Here's what I get:

p [1,3,5].inject_with_index{|sum, (part, index)| sum + part}
=> seconderc.rb:46:in `+': can't convert Fixnum into Array (TypeError)

p [1,3,5].inject_with_index{|sum, part, index| sum + part}
=> [1, 0, 3, 1, 5, 2]


My own inject is a lot clunkier (and takes no params) but seems to work:

def inject_with_index
 total = self[0]
 index = 1
 loop do
   break if index == self.length
   total = yield(total, self[index], index)
   index += 1
 end
 total
end
public :inject_with_index

p [1,3,5].inject_with_index{|sum, part, index| sum + part}

=> 9


Les