From: dblack@...
Date: 2007-07-23T06:11:11+09:00
Subject: Re: Syntax bug, in 1.8.5?  return not (some expr) <-- syntax error vs return (not (some expr)) <-- fine

Hi --

On Mon, 23 Jul 2007, Good Night Moon wrote:

> On Sun, 22 Jul 2007 16:51:26 +0900, Sharon Phillips wrote:
>> There's a difference between [not, and, or] and [!, &&, ||] Not sure
>> what it is, but I've found it better to use the latter. Still, if you
>> wrap the whole statement in another set of brackets (like
>> intersects_good) it will work.
>>
>>    def intersects_bad(other)
>>      return (not ((other.x1 < self.x0 or self.x1 < other.x0) and
>>                   (other.y1 < self.y0 or self.y1 < other.y0)))
>>    end
>>
>> by the way, what's the difference between the two methods? They appear
>> identical.
>
> Thanks. The difference is just to point out what looks like
> a bug; the parens shouldn't make a difference. Look at
> my other reply in this thread for elaboration.

I don't think it's a bug.  Have a look at these examples:

def x; return 1 and puts "I'm gone!"; end
SyntaxError: compile error
(irb):3: void value expression

def x; 2 not 3; end
SyntaxError: compile error
(irb):5: syntax error, unexpected kNOT, expecting kEND

These both make sense.  'and' is right-associative, so you're trying
to do something after having already returned, which doesn't work.
And in general you can't do "x not y", which is what "return not ..."
is read as.


David

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