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)
    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