Print Function

If we are running programs from the command line we might want them to output some data, rather than just define functions and other values. We can add a print function to our Lisp which makes use of our existing lval_print function.

This function prints each argument separated by a space and then prints a newline character to finish. It returns the empty expression.

lval* builtin_print(lenv* e, lval* a) {
  /* Print each argument followed by a space */
  for (int i = 0; i < a->count; i++) {
    lval_print(a->cell[i]); putchar(' ');
  }
  /* Print a newline and delete arguments */
  putchar('\n');
  lval_del(a);
  return lval_sexpr();
}