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From: Ruvim <ruvim...@gmail.com>
Newsgroups: comp.lang.forth
Subject: Re: Recognizers and postponing
Date: Mon, 29 Jun 2020 17:45:56 +0300
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On 2020-06-29 15:33, Ruvim wrote:
> On 2020-06-28 18:30, Anton Ertl wrote:
[...]
>> : foo ]] "foo bar" type [[ ; immediate
>> : bar foo ;
>> bar
>>
>> works exactly like the version using POSTPONE above.
>>
>> It would take extra code to make it work differently.
> 
> Yes. But it worth it.
> 
> 
> The following implementation for "]] ... [[" construct covers the most 
> practical cases of your implementation and does not use the "postpone 
> action" from a token descriptor at all! Do we really need this action?
> 
> 
>    : xt, compile, ;
> 
>    : compile-compile-token? ( k*x td -- true | k*x td false )
>      td-nt over = if drop name>compile swap lit, xt, true exit then
>      token>xt? if lit, 'xt, xt, true exit then
>      postpone [: compile-token postpone ;] 'xt, xt, true

A correction for the line above, to make the data stack transparent:

   depth >r postpone [: depth r> - n>r
     compile-token
   nr> drop postpone ;] 'xt, xt, true


>      \ There is a possibility to return false
>      \ for some implementation defined cases
>    ;
>    : next-lexeme ( -- c-addr u|0 )
>      begin parse-name ?ET ( addr ) refill ?E0 drop again
>    ;
>    : ]]
>      begin next-lexeme 2dup "[[" equals 0= while
>        recognize-any dup ?nf compile-compile-token?
>        0= -32 and throw
>      repeat 2drop
>    ;