K combinator - Lazy evaluation, C++ (clang)

K combinator - Lazy evaluation

#include <assert.h>
#include <stdio.h>
#define STACK_SIZE 50000

/* a boxed value is a function that can be executed to compute something. */
typedef void (*Boxed)();

/* a return continuation that receives a boxed value. */
typedef void (*BoxedContinuation)(Boxed);

/* A return continuation that receives an int value. */
typedef void (*IntContinuation)(int);

/* Custom stack allocated on the .data section*/
void *stack[STACK_SIZE];

/* Stack pointer */
int sp = 0;

/* Push a continuation `cont` */
void pushContinuation(void *cont) {
    assert(sp >= 0);
    assert(sp < STACK_SIZE);
    stack[sp] = cont;
    sp++;
}

/* Pop a continuation frame. */
void *popContinuation() {
    assert(sp < STACK_SIZE);
    assert(sp >= 0);
    sp--;
    void *cont = stack[sp];
    return cont;
}

/* one = 1# */
void one() {
    printf("in function: %s\n", __FUNCTION__);
    void *f = popContinuation();
    (*(IntContinuation)(f))(1);
}

/* bottom = bottom */
void bottom() {
    printf("in function: %s\n", __FUNCTION__);
    bottom();
}

/* K x y = x */
void K(Boxed x, Boxed y) {
    printf("in function: %s\n", __FUNCTION__);
    void *f = popContinuation();
    (*(BoxedContinuation)(f))(x);
}

void XForceContinuation(int i) {
    printf("in function: %s\n", __FUNCTION__);
    printf("%d", i);
}

void KContinuation(Boxed x) {
    printf("in function: %s\n", __FUNCTION__);
    pushContinuation((void *)XForceContinuation);
    x();
}

int main() {
    printf("in function: %s\n", __FUNCTION__);
    pushContinuation((void *)KContinuation);
    K(one, bottom);
    return 1;
}


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