Re: List functions

[Hans Aberg <haberg-1@telia.com>]

On 2 Dec 2010, at 10:57, Marco Maggi wrote:

>> I am  writing on a parser that  translates normal function
>> syntax in to Guile code.
>
> I do not know which scenario you are working with, ...

I have a Bison/Flex parser/lexer combination that writes Guile code  
directly by calling Guile C-functions, some via C++ wrap I wrote. The  
expressions are not evaluated until after the construction, just as  
when one enter expressions in the Guile interpreter, which gives  
greater flexibility.

So I am not limited by any syntax, only the Guile semantics, which is  
more general than that of Scheme, in view of that one by calling C- 
functions, one can build things that not possible in Scheme proper. By  
writing out the expression before evaluation, I get a Guile code  
expression.

I think I may be able to solve the original problem. I am now thinking  
by making functions that are called as (f (x y) z), where some  
arguments are lists, which correspond to Haskell
   f (1, 2) 3 where f (x, y) z = x + y + z
   --> 6



> ...but it is
> perfectly possible to convert the input syntax:
>
>  ((sin , cos , tan) 1.2)
>
> to the output:
>
>  ((lambda args
>     (map (lambda (f)
>            (apply f args))
>       (list sin cos tan)))
>   1.2)
>
> if you accept to write  the input syntax expressions only as
> part of a  macro use, let's call this macro  H; so the macro
> use:
>
>  (h
>   ((sin , cos) 1.2))
>
> can be expanded to:
>
>  ((lambda args
>     (map (lambda (f)
>            (apply f args))
>       (list sin cos tan)))
>   1.2)
>
>  It is  also possible  to write the  H macro such  that any
> expression with nested expressions  can appear in its use; H
> can be  made just  like the built  in syntax BEGIN  but with
> syntax different from standard Scheme.  Example:
>
>  (h
>   (display (+ 4 ((sin , cos) 1.2))))
>
>  Once  you have  H you  can write  a DEFINE/H  syntax which
> works just like the standard  DEFINE but accepts in its body
> the modified syntax:
>
>  (define/h (doit x y)
>   (display (+ x ((sin , cos) y))))
>
>  The tool to do it is the syntax-case macro system.
>
> HTH
> -- 
> Marco Maggi