TCO

tco.c

#include "tco.h"
#include <stdlib.h>
#include <stdarg.h>

conscell cons_f(void *car, void *cdr)
{
	conscell ret = malloc(sizeof(struct conscell_str));

	ret->car = car;
	ret->cdr = cdr;

	return ret;
}

#define MAXARGS 31

tco.h

#ifndef TCO_H_
#define TCO_H_

#include "stdarg.h"

void (*nextfun)(void *);
void *nextarg;

#define CALL(fun, arg) \
	do { \
		nextfun = fun; \
		nextarg = arg; \
		while(nextfun) \
			nextfun(nextarg); \
	} while(0);


#define CALL2(fun, arg) \
	do { \
		nextfun = fun; \
		nextarg = arg; \
		return; \
	} while(0);

#define RETURN CALL2(NULL, NULL)

typedef struct conscell_str {
	void *car;
	void *cdr;
} *conscell;


#define cons(x, y) cons_f((void *)x, (void *)y)
conscell cons_f(void *car, void *cdr);

#define car(x) ((conscell)x)->car
#define cdr(x) ((conscell)x)->cdr
#define integer(x) (uint64_t)(x)

/*conscell list(...); */

#endif

test.c

#include <stdio.h>
#include <unistd.h>
#include <stdint.h>
#include "tco.h"

void print_sums(void *);

int main()
{
	uint64_t i; /* 64 bit machine */

	conscell c = NULL;

	for(i=50; i>0; i--)
		c = cons(i,c);

	CALL(print_sums, c);

	return 0;
}


/* recursive (tail call optimized) */
void print_sums(void * n)
{
	conscell c = (conscell)n;

	printf("count: %ld\n", integer(car(c)));

	if(cdr(c) && cdr(cdr(c)))
		CALL2(print_sums,
			cons(
				integer(car(c)) + integer(car(cdr(c))),
				cdr(cdr(c))));

	RETURN;
}