scheme parser

/* Convert the list of tokens to a cons cell */
/* tokens have a "type" (one of NUMBER, NUMBER_FLT, STRING, SYMBOL, LPAREN, RPAREN) */
struct cons *tok_to_cons(struct tokens *tok)
{
  struct tokens *node = tok;
  struct cons *cell = malloc(sizeof(struct cons *));
  struct cons *head = cell;
  node = node->next;
  int *integer = NULL;
  float *fl = NULL;

  while (node != NULL) {
    object_t *obj = (node->type != RPAREN) ? malloc(sizeof(object_t *)) : NULL;
    /* Similarly, objects also have a type, except they cannot be (L|R)PAREN */
    switch(node->type) {
      case NUMBER:
        integer = malloc(sizeof(int *));
        *integer = atoi(node->str);
        obj->val = (void *)integer;
        break;
      case NUMBER_FLT:
        fl = malloc(sizeof(float *));
        *fl = atof(node->str);
        obj->val = (void *)fl;
        break;
      case SYMBOL:
        obj->val = (char *)strdup(node->str);
        break;
      case LPAREN:
        /* Entering a nested cell */
        /* For reference, (a . (b . ((c . (d . nil)) . nil))) = (a b (c d)) */
        obj->val = tok_to_cons(node);
        break;
      case RPAREN:
        /* Reached end of cons cell */
        head->cdr = NULL;
        return cell;
      case STRING:
        obj->val = strdup(node->str);
        break;
    }
    obj->type = node->type;
    head->car = obj;
    head->cdr = malloc(sizeof(struct cons *));
    node = node->next;
  }
}