From: "David A. Black" <dblack@...>
Date: 2005-02-14T00:11:51+09:00
Subject: Re: evaluation order

Hi --

On Sun, 13 Feb 2005, Martin DeMello wrote:

> David A. Black <dblack@wobblini.net> wrote:
>
>> (For clarity I've deleted the warning about using '=' in conditional.
>> [Matz, can't we get rid of that warning?])
>
> I'd love per-warning suppressibility, but if not, I think this particular
> one does more good than harm. (But then, I find the if (a = f(x)) idiom
> rather ugly to begin with).

I'm trying to figure out the pattern behind when it gets triggered or
not:

   irb(main):002:0> while (x = 1); end
   (irb):2: warning: found = in conditional, should be ==
   irb(main):003:0> while (line = gets); end
   abc
   ^D
   => nil
   irb(main):004:0> if (m = /a/.match("b")); end
   => nil
   irb(main):005:0> if (m = /a/); end
   (irb):5: warning: found = in conditional, should be ==
   irb(main):006:0> if (m = "abc".replace("abc")); end
   => nil
   irb(main):007:0> if (m = "abc"); end
   (irb):7: warning: found = in conditional, should be ==
   => nil

When the rhs is a literal, I guess?  That at least vastly increases
the chances of its being a case of a typo.  Could it be that Matz is
several steps ahead of me? :-)


David

-- 
David A. Black
dblack@wobblini.net