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From: Ruvim <ruvim.pinka@gmail.com>
Newsgroups: comp.lang.forth
Subject: Standard compliance for systems (was: single-xt approach in the
 standard)
Date: Mon, 23 Sep 2024 10:56:46 +0400
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On 2024-09-23 09:28, dxf wrote:
> On 23/09/2024 2:57 am, Ruvim wrote:
....
>> NB: Keeping floating-point numbers on the data stack does not make a Forth system non-standard, but it merely adds an environmental restriction to this system, see the section "12.4.1.4 Environmental restrictions" in Forth-2012.
> 
> I hadn't seen that.  Forth-94 stated floating-point stack was "the default".
> If the only change is that the latter is clarified, then no harm done.
> Implementing separate stack on an 8-bit cpu would be expensive and a
> performance killer.  

> As to being "far simpler" to program, similar appeals
> are made in respect of locals.
> I make it a point to program as if I had a
> unified stack just to see if the claim is true.

A real problem was to create programs that work with floating point 
numbers and would work correctly both on a unified fp stack and on a 
separate fp stack.

See the section "C.7.2 Separate Floating-point Stack is now Standard" in 
Forth-2012 <https://forth-standard.org/standard/diff#subsection.C.7.2>


> 
>> 2) Quote-delimited character interpretation ('A') makes programs simpler, this seems obvious.
> 
> Only thing obvious is it's an import from other languages and redundant.
> Forth Inc stated they didn't agree with it but eventually provided it.
> 

Using `'x'` is simpler and shorter than `[char] x` or `char x` depending 
on the context.

And even if you redefine `[char]` to provide the expected interpretation 
semantics, like:

   : [char] state @ if postpone [char] else char then ; immediate

`[char] x` is still longer than `'x'` and provides no additional benefit 
to programs.



>> 3) Two buffers for interpretive `s"` makes debugging simpler, because you can test words like `rename-file` interactively, see "A.17.3.4 Other transient regions" in Forth-2012.
> 
> I have  >PAD ( adr u -- adr2 u )  for that.  Uses existing resources and is
> more flexible.
> 

The phrase:

   s" foo" s" bar" rename-file .

is simpler than:

   s" foo" >pad s" bar" rename-file .

What advantages does the latter provide to users over the former?



If a Forth system is so limited in memory that it cannot provide two 
buffers for `s"`, it *might* provide only one buffer and declare the 
corresponding environmental restriction according to the sections:

- 5.1.1 System compliance
| An otherwise Standard System (Subset) that fails to comply
| with one or more of the minimum values or ranges specified
| in "3 Usage requirements" and its sub-sections has
| environmental restrictions.

- 5.1.2 System labeling
| The phrase "with Environmental Restrictions" shall be
| appended to the label of a Standard System (Subset) that
| has environmental restrictions.

- 11.3 Additional usage requirements, 11.3.4 Other transient regions
| The system provides transient buffers for `S"` and `S\"`
| regions strings. These buffers shall be no less than 80
| characters in length, and there shall be at least two buffers.




--
Ruvim