Path: csiph.com!usenet.pasdenom.info!aioe.org!.POSTED!not-for-mail
From: "Rod Pemberton" <dont_use_email@xnohavenotit.cnm>
Newsgroups: comp.lang.forth
Subject: Re: quick review of <BUILDS and CREATE history
Date: Mon, 20 Jan 2014 16:14:16 -0500
Organization: Aioe.org NNTP Server
Lines: 120
Message-ID: <op.w9z7x2uk5zc71u@localhost>
References: <op.w9x40in85zc71u@localhost> <zqqdnYChjNguw0HPnZ2dnUVZ_tednZ2d@supernews.com> <QfadnSaNy6ZL7kHPnZ2dnUVZ_sidnZ2d@supernews.com> <op.w9yu1gm65zc71u@localhost> <samdnZ0iro4aAkHPnZ2dnUVZ_t2dnZ2d@supernews.com> <op.w9yz3nnj5zc71u@localhost> <KbednR9Be4m-VUHPnZ2dnUVZ_rOdnZ2d@supernews.com>
NNTP-Posting-Host: CNsg4fVcCsvs3UaOgZtQCw.user.speranza.aioe.org
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii; format=flowed; delsp=yes
Content-Transfer-Encoding: 7bit
X-Complaints-To: abuse@aioe.org
User-Agent: Opera Mail/12.16 (Linux)
X-Notice: Filtered by postfilter v. 0.8.2
Xref: csiph.com comp.lang.forth:27979

On Mon, 20 Jan 2014 01:54:25 -0500, Elizabeth D Rather <erather@forth.com>  
wrote:

> On 1/19/2014 7:27 PM, Rod Pemberton wrote:

> I'm baffled. CREATE makes a header; :NONAME doesn't. CREATE
> doesn't turn on the compiler. :NONAME does. These differences
> are critical, not trivial.
>

Based on your post and Mark's, I think my :NONAME is functioning
like :NONAME combined with HEADER.

>>> It sounds as though you have a very
>>> mistaken notion of what :NONAME does.
>>
>> AIUI, :NONAME is the same as : except it doesn't install
>> a name into the dictionary header of the word being defined
>> and it returns an xt.  It's definition is terminated by
>> a ; just like a : definition.  It compiles a definition
>> just like a : definition.
>>
>> In most Forths, : calls CREATE to build the header
>> and insert the name the word being defined.  After
>> CREATE is finished, the colon definition continues
>> compiling until ; .
>
> In most Forths that I'm familiar with, : calls a lower-level word to
> build the header and insert the name. CREATE also calls that. However,
> CREATE does *not* "continue compiling", instead it sets the default
> action of the word just created to DODOES or equivalent with an
> associated data location. : has no associated data location. In other
> words, the only thing both : and CREATE share is a call to the
> lower-level word to make the header.
>

Let me break down what I'm doing currently.
It's been a while since I've read/coded the code,
so hopefully, no misunderstandings/mistakes posted...
This is what :NONAME CREATE : and ; are doing:

:NONAME
-the next few steps creates a dictionary header
--blanks name field area (NFA)
--updates link field address (LFA) with LAST
--updates dictionary bits (part of NFA)
--updates LAST
--updates dictionary pointer (DP) to code field address (CFA)
-puts HERE (at current CFA) on the stack for use as an XT
-compiles ENTER into the definition (at current CFA)
-turns on compiling ]
-SMUDGEs the definition being compiled (turns on)

:
-executes :NONAME
-executes BL WORD to get name of definition
-executes COUNT
-sets up values for CMOVE which consumes :NONAMEs XT
-finds the name field (NFA)
-executes CMOVE to move the definition's name into the name field

;
-compiles EXIT into a definition
-SMUDGEs the definition being compiled (turns off)
-turns off compiling [

CREATE
-executes :
-places HERE on the stack
-executes ;
-sets the dictionary pointer (DP) to code field address (CFA)
-stores DOVAR into the code field address (CFA)
-resets dictionary pointer (DP) to saved HERE on stack


> Consider the definition:
>
> : CONSTANT ( n -- )   CREATE ,
>     DOES> ( -- n ) @ ;
>
> Here CREATE builds the header and , compiles the value in data space.
> The fact that compiling continues is not due to CREATE, which has
> finished executing, but to : which invoked CREATE and , and continued
> compiling.
>

All the common definitions which use CREATE work correctly.

>> AIUI, all I've done is switch things around to build
>> : up from :NONAME instead of using CREATE.  If it's
>> correct, which I believe it is, <BUILDS can be built
>> from :NONAME also.
>
> <BUILDS and CREATE need to do two things that :NONAME
> does not: build a header, and associate a data space
> address. :NONAME turns on the compiler and records the
> *code space* location of the associated xt,
> neither of which <BUILDS or CREATE do.
>
> They have *nothing* in common.
>
> The distinction between code space and data space is critical
> when you're dealing with RAM/FLASH architectures.
>

Okay, I suspect you're going to tell me to remove the header
creation in :NONAME and place it into a word named HEADER
or (CREATE).  Then, have : call HEADER or (CREATE).

So, then, the rough definition for : would become:
: HEADER :NONAME BL WORD COUNT ... "get NFA" CMOVE ;

I'm assuming the rest is acceptable ... ?

IIRC, :NONAME on my system needed a header for the dictionary
to be linked together correctly.  If so, I'll have to check
into why that is...  It's probably wise to fix the issue.


Rod Pemberton