On Fri, Jan 30, 2004 at 12:52:42AM -0600, Brian Hurt wrote:
[snip]
> 
> Technically, he's correct.  What C doesn't have is partial function 
> application, which makes having functional types much less worthwhile- 
> it's impossible for a function type to also contain state.  Which is why 
> when I do callbacks in C, I always include a void * context which is 
> passed (uninspected) to the callback routine.
> 
> I mean, writting this function in C would be interesting to say the least:
> 
> let summer ival =
>     let cval = ref ival in
>     let f x = cval := !cval + x; !cval in
>     f
> ;;

OK, maybe C doesn't support it, but it's easy to do this one in C++:

#include <assert.h>

class summer
{
  int cval;
public:
  summer(int ival): cval(ival) {} 
  int operator()(int x) { cval += x; return cval; }
};

int main()
{
  summer s(3);
  assert(s(2)==5);
  assert(s(7)==12);
  return 0;
}

Issac

[snip]

-- 
Issac Trotts
http://redwood.ucdavis.edu/~issac

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