[plt-scheme] macro expension order

The problem is: to _compile_ SML code into PLT Scheme, not to manually 
translate ML.

According to SML syntax, in (list NONE n), there is no obvious 
difference bewetween NONE and n: they are both normal symbol.

Chongkai

Jens Axel Søgaard wrote:
> Chongkai Zhu skrev:
>> Hi all,
>>
>> I have the following program;
>>
>>  (define-syntax NONE (syntax-id-rules () (NONE 'NONE)))
>>  (define-syntax SOME (syntax-rules () ((SOME g57951) (list 'SOME 
>> g57951))))
>>  (define expt
>>    (match-lambda*
>>      ((list NONE n) (expt (SOME 2) n))
>>      ((list (list 'SOME b) 0) 1)
>>      ((list (list 'SOME b) n) (if (= (mod n 2) 0) (expt (SOME (* b 
>> b)) (/ n 2)) (* b (expt (SOME b) (- n 1)))))))
>>
>> It is automatically translated from the following SML program:
>>
>> datatype 'a option = NONE | SOME of 'a
>>
>> fun expt (NONE, n) = expt (SOME 2, n)
>>   | expt (SOME b, 0) = 1
>>   | expt (SOME b, n) =
>>     if n mod 2 = 0 then
>>        expt (SOME (b*b), n div 2)
>>     else
>>        b * expt (SOME b, n-1)
>
>
> Why not represent NONE and SOME as structures?
>
> (define-struct NONE ())
> (define-struct SOME (b))
>
> (require (lib "plt-match.ss"))
>
> (define expt
>   (match-lambda*
>     [(list (struct NONE ()))
>      (expt (make-SOME 2) n)]
>     [(list (struct SOME (b)) 0)
>      1]
>     [(list (struct SOME (b)) n)
>      (if (= (modulo n 2) 0)
>          (expt (make-SOME (* b b)) (quotient n 2))
>          (* b (expt (make-SOME b) (- n 1))))]))
>
> (expt (make-SOME 2) 0) ; => 1
> (expt (make-SOME 2) 1) ; => 2
> (expt (make-SOME 2) 2) ; => 4
> (expt (make-SOME 2) 3) ; => 8
>
>