From: Eric Hodel <drbrain@...7.net>
Date: 2006-02-07T16:36:49+09:00
Subject: Re: ANDCALL / iff? / &? (was Re: ruby-dev summary 28206-28273)

On Feb 6, 2006, at 6:09 PM, Eero Saynatkari wrote:

> On 2006.02.07 10:03, Evan Webb wrote:
>> if t = a[0] and t.strip.empty?
>>    # jump off a bridge
>> end
>
> A minor nitpick, you need
>
>   if (t = something.first) and t.strip.empty?
>     # ...
>   end
>
> Otherwise a warning will be emitted (sensible behaviour).

$ ruby -vwe 'a = ""; if t = a[0] and t.strip.empty? then end'
ruby 1.8.4 (2005-12-24) [powerpc-darwin8.4.0]
$ ruby -vwe '0 if a = 1; 0 if a = 1.1; 0 if a = nil; 0 if a = true; 0  
if a = false; 0 if a = ""'
ruby 1.8.4 (2005-12-24) [powerpc-darwin8.4.0]
-e:1: warning: found = in conditional, should be ==
-e:1: warning: found = in conditional, should be ==
-e:1: warning: found = in conditional, should be ==
-e:1: warning: found = in conditional, should be ==
-e:1: warning: found = in conditional, should be ==
-e:1: warning: found = in conditional, should be ==

$ ruby -vwe 'if (a, b = 1, 2) then end'
ruby 1.8.4 (2005-12-24) [powerpc-darwin8.4.0]
-e:1: multiple assignment in conditional

Those are the only cases that give a warning for assignment in  
conditional.

1.6.1 and earlier warned for all assignments in conditionals, see  
parse.y 1.61.

-- 
Eric Hodel - drbrain@segment7.net - http://segment7.net
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