From: oinkoink+unet@... (Bret Jolly)
Date: 2004-01-15T04:11:39+09:00
Subject: Re: Warnings on assignments in conditionals?

David Heinemeier Hansson <david@loudthinking.com> wrote in message news:<8609BD15-45EF-11D8-A416-000A958E6254@loudthinking.com>...
> I consider the following statements to be perfectly legit (although 
> perhaps slightly ambigious) and Ruby does obey, but throws this 
> mandating warning. Am I just being paranoid or is Ruby forcing a style 
> upon me :)?
> 
> irb(main):008:0> if a = 1 then true else false end
> (irb):8: warning: found = in conditional, should be ==
> => true
> irb(main):009:0> a
> => 1
> 
> irb(main):010:0> if a = nil then true else false end
> (irb):10: warning: found = in conditional, should be ==
> => false
> irb(main):011:0> a
> => nil

  But this C idiom really doesn't make much sense in Ruby, since
in Ruby 0 is true in a boolean context.  You might want to say
something like:
          if not (a = c).nil? then foo else bar end
but what you have is almost certainly either an error or at least
stylistically dubious. So yes, I guess Ruby is forcing a style on
you.  I think that if you really want something like this, the Ruby
way would be to define a method 'true?' for objects:
class Object
 def true?
   if nil? or self == false then return false end
   true
 end
 def false?
   not true?
 end
end

then write:
       if  (a = c).true? then foo else bar end

Oinkful Regards, Bret