#include <stdio.h>
#include <stdlib.h>

#include "inttypes.h"
#include "wscm.h"

// cons lists
O cons(O head, O tail) {
  I mark = rootmark();
  addroot(&head);
  addroot(&tail);

  const Z sz = sizeof(H) + sizeof(C);
  H *h = alloc(sz);
  h->size = sz;
  h->type = OBJ_CONS;

  C *c = (C *)(h + 1);
  c->head = head;
  c->tail = tail;

  rootreset(mark);
  return BOX(h);
}

C *uncons(O obj) {
  if (obj == NIL)
    return NULL;
  if (IMM(obj)) {
    fprintf(stderr, "unpair: expected pair, got integer\n");
    abort();
  }
  H *h = UNBOX(obj);
  if (h->type != OBJ_CONS) {
    fprintf(stderr, "unpair: expected pair, got type %" PRIdPTR "\n", h->type);
    abort();
  }
  return (C *)(h + 1);
}