Re: extending FEM enginering package with Guile

[Mario Storti]

>>>>> On Mon, 05 Jan 2004 16:20:17 -0300, 
>>>>>      Mario Storti <address@hidden> said:

> I'm discovering Guile, and I found it very exciting. I'm writing a GPL
> C++ Finite Element code (see http://venus.ceride.gov.ar/petscfem
> ...

Thanks to all answering my posting. 

>>>>> On Mon, 05 Jan 2004 15:26:09 -0500, 
>>>>>      address@hidden (Paul Jarc) said:

> Mario Storti <address@hidden> wrote:
>> the lack of `break' and `continue' in Scheme.

> Guile has break and continue (undocumented in the 1.6.4 manual ), but
> they are only defined inside the body of the while loop, not at the
> top level.  (Well, there is a break procedure from srfi-1, but that
> does something different.)

OK. That seems to be what I expected. I couldn't get `continue' and
`break' working in 1.6.4 and I couldn't compile 1.7.0 (errors in
configure about the GMP library). Then I have taken the `while'
definition from `boot-9.scm' in 1.7.0 and inserted it directly in my
code (with a minor modification, since `make-symbol' is not available
in 1.6.4.). So I have now a working `while-continue-break' macro. This
is a warkaround until a new stable release comes out. 

>>>>> On Mon, 5 Jan 2004 23:04:14 +0100, 
>>>>>      address@hidden said:

> Well, scheme has a rather powerfull syntax facility, you can (and probably
> should) write syntactic extensions that match your users needs/expectations.
> With the help of macros (esp syntax-case e.a.) you can create your domain
> specific "little language". After all, this is one of the reasons why
> the FSF did choose scheme as their future embedable scripting language.

>> while (cond0) {
>> // body1 0;
>> // ...
>> if (cond1) break;
>> // body 1
>> // ...
>> if (cond2) continue;
>> // body 2
>> // ...      
>> }
>> 
>> are hard to write, due to the lack of `break' and `continue' in
>> Scheme. I think that one can do that with catch/throw bu it also seems
>> an overkill. I found some flame wars between some other Lisp dialects
>> and Scheme and I anticipate that I'm not interested in starting such a
>> discussion. So:

Yes, I see that very powerful macros can be written. 

> Well, scheme has a rather powerfull syntax facility, you can (and probably
> should) write syntactic extensions that match your users needs/expectations.
> With the help of macros (esp syntax-case e.a.) you can create your domain
> specific "little language". After all, this is one of the reasons why
> the FSF did choose scheme as their future embedable scripting language.

> Flame wars aside, if there is a need for such a syntax it can be implemented.
> Heinrich Taube (of Common Lisp Music fame) wrote a guile version of Common
> Lisp's loop macro -- i think i once hacked up a guile module wrapper for it.
> With that code you can do things like:

>  (use-modules (clm iter))

>  (define (all-squares-upto number)
>    (loop for n in (iota number)
>          collect (* n n)))

>  (loop for language in '(perl python java cobol)
>        do (format #f "~A sucks!" language))

>  ;; break out of a loop
>  (loop while (= (remainder (current-time ) 2) 0)
>        do (format #t "Not yet ~%"))
> etc. etc.
> If you want i can try to find my wrapper and put it online.

>  Ralf Mattes

Thanks. I think that with the `while-continue-break' to be included in
next releases is enough. 

Mario

-------------------------
Mario Alberto Storti
CIMEC (INTEC/CONICET-UNL), Guemes 3450 - 3000 Santa Fe, Argentina
Tel/Fax: +54-342-4511594 e-mail: address@hidden
http://www.cimec.org.ar/mstorti, http://www.cimec.org.ar
-------------------------