From: AppleII717 <salex@...>
Date: 2010-08-18T07:50:07+09:00
Subject: Strange behavior of or condition in loop

I don't understand why ruby's "or" acts differently in a loop.

This is some code I pulled out of a rails model, expanded the
assignments and simulated in IRB (1.8.7 and 1.9.2rc)

#simple boolean assignments
#Why does this work

  dirty = false
  found = true
  dirty = dirty or found
  puts dirty.to_s  => true

#same type of assignments in loop giving meaning to dirty and found
  #But this does not

  a = ["score_method", "updated_at"]
  dirty = false
  a.each{|attrib|
    puts dirty.to_s + " in "
    found = !( /score_method|weight|critical|minimum_value/i =~
attrib ).nil?
    dirty = dirty or found
    puts dirty.to_s + " out " + found.to_s
  }
  puts dirty.to_s => false

#another version with parens  around or
  #But this does

  a = ["score_method", "updated_at"]
  dirty = false
  a.each{|attrib|
    puts dirty.to_s + " in "
    found = !( /score_method|weight|critical|minimum_value/i =~
attrib ).nil?
    dirty = (dirty or found)
    puts dirty.to_s + " out " + found.to_s
  }
  puts dirty.to_s => true


I've been doing to additive boolean assignment stuff forever without
parens. Guess I just don't understand Ruby.