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From: dwp@willett.pgh.pa.us (Doug Philips)
Newsgroups: comp.lang.forth
Subject: Re: Puzzle?  What Puzzle?
Message-ID: <1677.UUL1.3#5129@willett.pgh.pa.us>
Date: 6 Sep 90 03:43:12 GMT
References: <12511@sdcc6.ucsd.edu>
Organization: String, Scotch tape, and Paperclips.  (in Pgh, PA)
Lines: 49

In <12511@sdcc6.ucsd.edu>, ir230@sdcc6.ucsd.edu (john wavrik) writes:
[Since its been a while, I'm quoting more of this than I usually
 would. -dwp]

> Here is the situation:
>           In most versions of Forth, the size of the return 
>           stack can be temporarily extended -- to permit the 
>           running of recursive algorithms when desired -- but 
>           the mechanism has not been standardized. 
> 
>           On a special class of Forths (those on Forth machines) 
>           there are inherent reasons why the size of the return 
>           stack cannot be altered. 
> 
> What do we do? 
> 
>    Do we recognize that Forth machines have been designed for a 
>    special type of computing -- but that it is desirable to provide 
>    this option  (and you might as well throw in SP0 etc) when 
>    possible. 
>                                  OR 
> 
>    Do we say that because a special class of machines is not suited 
>    for recursion, Forth in general will not be suited for recursion. 
> 
> The ANS-Forth approach to language standardization is to choose the 
> second alternative.
> 
> The effect of dragging everything down to the lowest common 
> denominator is to spread limitations rather than accentuate strengths.
> If the Forth machines are, in fact, a special class of machines that 
> have their own rules I see nothing that inherently prevents a Standard
> from specifying a different form of behavior for this special class.

If there are some machines on which you cannot extend the return stack,
then doing so makes a program not portable.  How not portable depends on
the number of restrictive machines.  I don't have any figures, but
apparently the TC feels that there are enough of them to make this an
issue.  I see nothing wrong with making this an environmental dependancy in
your program.  I'm not sure how to handle the extended wordset (were I to
propose one).  It seems kind of silly to propose an extended wordset for
one word ( CHANGESTACKSIZE ), but equally silly to have a catchall wordset
instead.

-Doug

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