From: Matthew Kerwin <lists@...>
Date: 2013-07-18T07:55:12+09:00
Subject: Re: Iteration anomalu

Sascha Abel wrote in post #1115792:
> Just try
>
> for i in [0..a.length] do
>   print i
> end
>
> and you should have your answer.

And to expand, in case it's not entirely clear:

* [x..y]  constructs an Array with one element, and
          that element is a Range
* Array#[]  accepts a Range parameter

  for i in [0..a.length]
    i     # i == (0..a.length)
    a[i]  # same as:  a[0..a.length]
  end

I believe you want to do this:

  for i in 0..a.length do #<-- no brackets!
    print a[i], "\n"
  end

However, to be honest, this is one of the only times I've ever seen a
"for" loop written in Ruby code.  The more typical, paradigmatic
approach would be:

  a.each do |el|
    print el, "\n"
  end

... and for the nested iteration:

  a.each_index do |i|
    a[i+1..-1].each_with_index do |cell,j|
      # processing on `cell` or `j`...
    end
  end

... or something like that.
Also note that you can call .each on a range, e.g.:

  (0...a.length).each do |i| ...

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