The implementation of S, in GForth

lehs

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Oct 22, 2016, 9:55:50 AM10/22/16

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In GForth S, is implemented with an final align

see s,
: S,
here noop 1+ allot place align ; ok

that seems unnecessary. Suppose you want to store several counted strings in the same array, then there would be an easy way to recall the i:th string in the array by

: nextword \ ad -- ad'
dup c@ + 1+ ;

: word# \ array i -- ad n
over @ mod 0
rot cell+ -rot
?do nextword loop count ;

if the strings would have been stored without trailing blanks.
So why this ALIGN?

HAA

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Oct 23, 2016, 1:45:33 AM10/23/16

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If it's any comfort VFX, SWF, Win32F all have their own variations on this.

Doug Hoffman

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Oct 23, 2016, 5:11:36 AM10/23/16

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On 10/22/16 9:55 AM, lehs wrote:
> In GForth S, is implemented with an final align
>
> see s,
> : S,
> here noop 1+ allot place align ; ok
>

> Suppose you want to store several counted strings in the same array,
> then there would be an easy way to recall the i:th string in the
> array by
>
> : nextword \ ad -- ad'
> dup c@ + 1+ ;
>
> : word# \ array i -- ad n
> over @ mod 0
> rot cell+ -rot
> ?do nextword loop count ;
>
> if the strings would have been stored without trailing blanks.
> So why this ALIGN?

In the Gforth 0.7.3 that I have S, is defined a bit differently.
Regardless, by modifying that to return the address of the string one
could simply store those addresses in a cell-based array.

: s, ( caddr len -- addr )
here dup >r over char+ allot place align r> ;

\ example use:

5 array a
s" Hello" s, 0 a !
s" foo" s, 1 a !
s" hello world" s, 2 a !

0 a @ count type \ => Hello
etc.

Or some variation of the above to do exactly what you want.

-Doug

Albert van der Horst

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Oct 23, 2016, 11:54:29 AM10/23/16

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In article <580c7df3$0$339$1472...@news.sunsite.dk>,

Doug Hoffman <glid...@gmail.com> wrote:
>On 10/22/16 9:55 AM, lehs wrote:
>> In GForth S, is implemented with an final align
>>
>> see s,
>> : S,
>> here noop 1+ allot place align ; ok
>>
>> Suppose you want to store several counted strings in the same array,
>> then there would be an easy way to recall the i:th string in the
>> array by
>>
>> : nextword \ ad -- ad'
>> dup c@ + 1+ ;
>>
>> : word# \ array i -- ad n
>> over @ mod 0
>> rot cell+ -rot
>> ?do nextword loop count ;
>>
>> if the strings would have been stored without trailing blanks.
>> So why this ALIGN?
>
>In the Gforth 0.7.3 that I have S, is defined a bit differently.
>Regardless, by modifying that to return the address of the string one
>could simply store those addresses in a cell-based array.
>
>: s, ( caddr len -- addr )
> here dup >r over char+ allot place align r> ;

A word like this is indispensible to implement a Forth kernel,
so probably every Forth has it. In ciforth it is called $, .

However all strings in ciforth have a cell count.
Using bytes really restrict the usability.

>
>\ example use:
>
>5 array a
>s" Hello" s, 0 a !
>s" foo" s, 1 a !
>s" hello world" s, 2 a !
>
>0 a @ count type \ => Hello
>etc.

With denotations (recognizers) I don't think it useful to have
volatile strings. So then you have

"Hello" 0 a 2!

(And if your strings are bd it isn't even visible)

>
>Or some variation of the above to do exactly what you want.
>
>-Doug

Groetjes Albert
--
Albert van der Horst, UTRECHT,THE NETHERLANDS
Economic growth -- being exponential -- ultimately falters.
albert@spe&ar&c.xs4all.nl &=n http://home.hccnet.nl/a.w.m.van.der.horst

lehs

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Oct 24, 2016, 5:10:24 AM10/24/16

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If you want an align you could put it there after, it's more convenient.

HAA

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Oct 25, 2016, 6:40:37 AM10/25/16

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lehs wrote:
> If you want an align you could put it there after, it's more convenient.

If your system's S, aligns do the same in your address calculation:

: nextword \ ad -- ad'
dup c@ + 1+ ALIGNED ;

lehs

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Oct 25, 2016, 8:59:57 AM10/25/16

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Yes that's also a solution. Thanks!