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NNTP-Posting-Date: Thu, 08 Nov 2012 14:29:52 -0600
From: Chris Hinsley <chris.hinsley@gmail.com>
Newsgroups: comp.lang.forth
Date: Thu, 8 Nov 2012 20:29:52 +0000
Message-ID: <2012110820295238952-chrishinsley@gmailcom>
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Subject: Re: Genral advise and comments on callback style words
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Xref: csiph.com comp.lang.forth:17182

On 2012-11-08 20:17:37 +0000, Chris Hinsley said:

> On 2012-11-08 20:04:06 +0000, Chris Hinsley said:
> 
>> On 2012-11-08 18:23:21 +0000, Josh Grams said:
>> 
>>> Chris Hinsley wrote: <2012110814515560672-chrishinsley@gmailcom>
>>>> On 2012-11-08 14:31:20 +0000, Chris Hinsley said:
>>>>>> Josh Grams wrote:
>>>>>>> 
>>>>>>> : LISTHEAD-ENUMERATE-FORWARDS ( u xt lh -- ln | 0 )
>>>>>>> 	TUCK  SWAP 2>R
>>>>>>> 	LISTHEAD-GET-HEAD BEGIN
>>>>>>> 		2DUP LISTNODE-GET-SUCC
>>>>>>> 	DUP WHILE
>>>>>>> 		2R@ EXECUTE
>>>>>>> 	?DUP UNTIL ELSE NIP THEN
>>>>>>> 	NIP NIP 2R> 2DROP ;
>>>>> 
>>>>> Err, I'm not sure that works! You are skipping the first node.
>>> 
>>> Yeah, sorry; I thought that's what your code was doing; see my response
>>> to your first reply to mine.
>>> 
>>>>> Isn't the 2DUP also blowing up the stack with an extra copy of the
>>>>> original LH each time ?
>>>> 
>>>> And it's not passing the user value into the callback at all ?
>>> 
>>> In this case, EXECUTE is ( u ln lh xt -- ln | 0 ), right?  So the 2DUP
>>> provides two of those four items, and the 2R@ provides the other two.
>>> 
>>> : LISTHEAD-ENUMERATE-FORWARDS ( u xt lh -- ln | 0 )
>>> 	TUCK  SWAP 2>R  LISTHEAD-GET-HEAD
>>> 	BEGIN DUP WHILE  ( u ln )  ( R: lh xt )
>>> 		2DUP LISTNODE-GET-SUCC 2SWAP
>>> 		2R@ EXECUTE
>>> 	?DUP UNTIL THEN ( u ln ln|0 ) NIP NIP 2R> 2DROP ;
>>> 
>>> --Josh
> 
> Ah, no that crashes ! Reason is that you end up processing the end of 
> list marker, ie the bottom two thirds of the listheader as if it was an 
> actual node ! Nice try ! ;)
> 
> Chris

This however does work, but leaves me debateing that single PICK and 
ROT verses the 2SWAP 2DUP and the extra NIP needed at the ELSE !

\ ( u xt lh -- r | 0 )
\ xt api is ( u ln lh -- r | 0 )
: LISTHEAD-ENUMERATE-FORWARDS
	SWAP OVER 2>R LISTHEAD-GET-HEAD
	BEGIN
		2DUP LISTNODE-GET-SUCC DUP
 	WHILE
 		2SWAP 2R@ EXECUTE ?DUP
 	UNTIL ELSE NIP THEN
 	2RDROP NIP NIP
;

Chris