Tamas K Papp  <tkpapp@gmail.com> wrote:
+---------------
| And of course you can have closures in any language if you fight hard
| for it, eg you can implement CL in C and then "have" closures in the
| latter.  Thinking about it, reimplementing CL in C is a much cleaner
| way to get closures than strugging with the brain-dead newLISP.
+---------------

Yup, viz.:

    $ cat ctest.c
    typedef unsigned long lispobj;   /* Or whatever your generic type is */

    typedef struct closure_s {
	lispobj (*func)(lispobj *, ...);
	lispobj *env;
    } closure_t, *closure_p;

    #define funcall_closure(closure, args...) \
      (((closure)->func)((closure)->env, ## args))

    #define CFUNCP lispobj (*)(lispobj *, ...)

    lispobj
    foo(lispobj *env, lispobj x, lispobj y)
    {
	return (env[0] * x) + (env[1] * y);
    }

    main()
    {
	lispobj e[2] = {3, 17};               /* Create a small environment */
	closure_t c = {(CFUNCP)&foo, &e[0]};  /* Close FOO over it. */

	printf("%d\n", funcall_closure(&c, 1, 1000));
    }
    $  make ctest
    cc -O -pipe   ctest.c  -o ctest
    $ ./ctest
    17003
    $ 

I've been playing these sorts of games for years, with great success!  ;-}

+---------------
| The mere suggestion that one should emulate closures
| by fiddling with lambda forms as lists reeks.
+---------------

Indeed!


-Rob

-----
Rob Warnock			<rpw3@rpw3.org>
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