From: "David A. Black" <dblack@...>
Date: 2009-10-05T19:23:41+09:00
Subject: [ruby-core:25939] Re: [Feature #2131] f(not x) => syntax error

Hi --

On Mon, 5 Oct 2009, James M. Lawrence wrote:

> Issue #2131 has been updated by James M. Lawrence.
>
>
> 09/23/2009 06:26 PM - Yukihiro Matsumoto:
>> |This should have been classified as a feature request.
>> |
>> |Since (not x) is legal syntax, it is my opinion that f(not x) should be legal.
>>
>> So, do you mean a,b,c = 1,2,3 is legal syntax, should we allow
>> f(a,b,c = 1,2,3) ?
>
> That (a,b,c = 1,2,3) and f(a,b,c = 1,2,3) contain different meanings
> inside the parens does not really affect my argument.
>
>  [0] + (a, b, c = 1, 2, 3)   # => [0, 1, 2, 3]
>
> Whether that should mean [0, a, b, 1, 2, 3] or something else is a
> different matter.
>
> My point is that the parens serve to disambiguate,
>
>  [0] + a, b, c = 1, 2, 3     # => syntax error
>  [0] + (a, b, c = 1, 2, 3)   # => [0, 1, 2, 3]
>  [0] + f a, b, c = 1, 2, 3   # => syntax error
>  [0] + f(a, b, c = 1, 2, 3)  # => ok
>
>  true | not false            # => syntax error
>  true | (not false)          # => true
>  true | f not false          # => syntax error
>  true | f(not false)         # => syntax error
>
> Why should the last case fail?  I also see no reason why
>
>  f(class Foo;attr_accessor :x;end;Foo.new.x=5)  # => syntax error
>
> should necessarily be illegal.  It's just f(5) with a side-effect.
> The parens are fully capable of capturing the expression.

One case that comes to mind is:

   f(class Foo; attr_accessor :x; end; Foo.new.x = 5,6)

Is 6 a second argument to f, or a second argument to Foo#x= ?


David

-- 
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