From: Matthew Moss <matt@...>
Date: 2008-11-26T06:30:50+09:00
Subject: Re: [QUIZ] Befunge (#184)


On Nov 25, 2008, at 11:15 AM, brabuhr@gmail.com wrote:

> On Tue, Nov 25, 2008 at 11:42 AM, Rob Biedenharn
> <Rob@agileconsultingllc.com> wrote:
>> On Nov 25, 2008, at 11:07 AM, brabuhr@gmail.com wrote:
>>> almost entirely untested) implementation built around define_method:
>>>
>>> bf.run #=> 3
>>
>> Seems like this program is:
>>
>> 1 1 + 2 3 + - .
>>
>> Which seems to be -3, not 3.  I think you have your args out of  
>> order.  Look
>> at how the non-commutative ops are defined.
>
> Yeah, that would be part of the entirely untested stuff ;-)
>
> %w{ + * }.each do |o|
>   define_method :"#{o}" do
>     a, b = @stack.pop, @stack.pop
>     @stack.push a.send(:"#{o}", b)
>   end
> end
> %w{ - / }.each do |o|
>   define_method :"#{o}" do
>     b, a = @stack.pop, @stack.pop
>     @stack.push a.send(:"#{o}", b)
>   end
> end

If you're going to fix the arg order of - and /, why wouldn't you do  
the same for + and *?

Popping b first, then a, isn't a workaround; it's the correct method  
according to spec. Why make + and * an exception to that?