NNTP-Posting-Date: Wed, 07 Nov 2012 07:56:26 -0600
From: Chris Hinsley <chris.hinsley@gmail.com>
Newsgroups: comp.lang.forth
Date: Wed, 7 Nov 2012 13:56:26 +0000
Message-ID: <2012110713562655972-chrishinsley@gmailcom>
References: <2012110713421835115-chrishinsley@gmailcom> <2012110713512322818-chrishinsley@gmailcom>
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Subject: Re: Genral advise and comments on callback style words
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On 2012-11-07 13:51:23 +0000, Chris Hinsley said:

> On 2012-11-07 13:42:18 +0000, Chris Hinsley said:
> 
>> Folks I have implamented an Amiga style double linked list words set a 
>> few days back and I have an emueration word as follows:
>> 
>> \ ( u xt lh -- ln | 0)
>> \ xt api is ( u ln lh -- ln | 0 )
>> : LISTHEAD-ENUMERATE-FORWARDS
>> 	0 >R
>> 	DUP LISTHEAD-GET-HEAD DUP
>> 	BEGIN
>> 		NIP DUP LISTNODE-GET-SUCC
>> 		DUP
>> 	WHILE
>> 		4 PICK 2 PICK 4 PICK
>> 		6 PICK EXECUTE DUP R!
>> 	UNTIL THEN
>> 	2DROP 2DROP DROP
>> 	R>
>> ;
>> 
>> This scans down the list until either it hits the end, or the callback 
>> for each node returns a value other than 0, that value is returned and 
>> the scan stops if it isn't 0 !
>> 
>> I'd like comments and advice on techniuqe, paticularly for things like 
>> the PICK stuff that gathers paramaters for each callback, and the use 
>> of the return stack for the returned value. Or if you just plain think 
>> I could code this a better way !
>> 
>> I'm not wanting to be pointed to "the novice package", thank you, but 
>> want this API as stated ! ;)
>> 
>> Regards all
>> 
>> Chris
> 
> I should also add that I wish to retain the 'look ahead' pointer to the 
> next node as the callback word must be allowed to remove or modify the 
> node it gets handed ! So the 'NIP DUP LISTNODE-GET-SUCC' is the bit 
> doing that.
> 
> Chris

Plus I do need to pass the list head into the callback, as they are 
allowed to add elements to the list as a result of scanning it etc. For 
example I have a 2D rectangle patch list and callbacks that can cut, 
paste or copy new patches to/from the list, as the callback slices and 
dices patches on the list new entires are add to the front of the list 
etc, and the current node can be removed entirely...

Chris