From: Jonathan Leighton <lists@...>
Date: 2006-01-29T22:39:26+09:00
Subject: Re: Loop weirdness

Okay, so let me get this right... if you do

foo.each { }

foo is re-evaluated with each iteration? Hence the bug? Why?

Jon

On Sun, 2006-01-29 at 22:06 +0900, Johan Veenstra wrote:
> Hmm interesting, I've added line number, couldn't explain it other wise:
> 
> def categorise(items)
>  1  categorised = []
>  2  add = proc { |item| categorised << { :num => item[:num], :items => [
> item[:foo] ] } }
>  3  items.each do |item|
>  4    if categorised.empty?
>  5      add.call(item)
>  6    else
>  7      categorised.each do |cat|
>  8        if cat[:num] == item[:num]
>  9          cat[:items] << item[:foo]
> 10          break
> 11        elsif cat == categorised.last
> 12          add.call(item)
> 13        end
> 14      end
> 15    end
> 16  end
> 17  categorised
> end
> 
> p categorise( [ { :num => 1, :foo => 'foo1' }, { :num => 45, :foo => 'foo45'
> } ] )
> 
> 1: categorised = []
> 3: first item( item[:num] == 1 )
> 4: categorised is empty
> 5: {:num=>1, :items=>["foo1"]} is added to categorised, so far so good
> 3: next item( item[:num] = 45 )
> 4: categorised is not empty
> 7: first category (cat[:num] == 1)
> 8: item[:num] is not equal to cat[:num] (45 != 1 )
> 11: cat is last category
> 12: { :num => 45, :foo => ['foo45'] } is added to categorised, just what we
> need
> 7: next category (yes there is a next category, number 45 that we've just
> added a moment ago) ( cat[:num] == 45)
> 8: added ['foo45'] to category 45, oh boy
> 10:break
> 3: no more items
> 18: return categorised
-- 
Jonathan Leighton
http://turnipspatch.com/ | http://jonathanleighton.com/ | http://digital-proof.org/