Re: [stack] function/object ambiguity + quotation alternative

----- Original Message ----- 
From: "John Nowak" <[email protected]>
To: <[email protected]>
Sent: Thursday, February 26, 2009 10:47 AM
Subject: Re: [stack] function/object ambiguity + quotation alternative


> 
> On Feb 26, 2009, at 10:21 AM, Stevan Apter wrote:
> 
>>> This strangeness is more evident in the following example. The
>>> expression '[dup swap] head' yields 'dup', but 'dup != [dup swap]
>>> head'! This is because the left side of the equality is the  
>>> *function*
>>> 'dup', but the right side gets reduced to the *object* 'dup'.
>>
>> i've always assumed that [dup swap] head is the function dup.  e.g.  
>> in XY:
>>
>>  2 [dup swap] first i
>> 2 2
>>
>> that is, [dup swap] first leaves the function dup on the stack.
>> then i moves the top item of the stack to the head of the queue.
>>
>> what am i missing?
> 
> I don't know XY, but XY does not work the same way as Joy and Factor  
> apparently.
> 
> Factor:
> 
>    >> 5 { dup } first call
>    Generic word call does not define a method for the word class.
>    Dispatching on object: dup
> 
> Joy:
> 
>    >> 5 [dup] first i
>    run time error: quotation as top parameter needed for i
> 
> This is the problem I'm referring to.
> 
> What XY does seems even worse though! Here's why:
> 
>    1. [dup] i == [dup] first i  (given, as per your example)


>    2. [dup] == [dup] first      (removing shared 'i' suffix)

no.  dup = [dup] first.

>    3. id == first               (removing share '[dup]' prefix)
> 
> Certainly first cannot be the identity function! Is the algebra of XY  
> broken? Am I missing something?
> 
> - John
>