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From: Ruvim <ruvim.pinka@gmail.com>
Newsgroups: comp.lang.forth
Subject: Re: Nested definitions
Date: Wed, 2 Jul 2025 20:58:17 +0400
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In-Reply-To: <2025Jul2.171200@mips.complang.tuwien.ac.at>

On 2025-07-02 19:12, Anton Ertl wrote:
> Ruvim <ruvim.pinka@gmail.com> writes:
>> On 2025-07-02 15:37, albert@spenarnc.xs4all.nl wrote:
>>> Or it has not even know it, if [ is smart enough to compile a jump to
>>> after ].
>>
>> This can be tricky because the following should work:
>>
>>    create foo [ 123 , ] [ 456 ,
>>
>>    : bar  [ ' foo compile, 123 lit, ] ;
> 
> Or something.  Anyway, [ and ] are used for a variety of purposes and
> trying to smarten them seems fraught with pitfalls.  If one really
> wants to have
> 
> : foo ... [ : bar ... ; ] ... ;
> 
> work, it may be better to put the smarts into : and ;.  E.g., on a
> system with sections, they could switch to another section and back.

Yes, and I wonder why introducing new words like `<:` and `;>` is better 
than putting the smarts into `:` and `;`.


> The benefit of defining a normal colon definition inside another colon
> definition eludes me, however.  Maybe mutual recursion, but the need
> is rare and deferred words handle that well.

As I can see, the idea is that the name of a nested definition has the 
limited scope — the same as a local variable, and it is not visible 
outside of the containing definition.


So, the program like:

   : foo
     ...
     [ : bar ... ; ]
     ...
     bar
     ...
   ;

Is equivalent to:

   get-current wordlist push-order definitions

     : bar ... ;

   set-current
     : foo
       ...
       bar
       ...
     ;
   previous




--
Ruvim