//: Calls can also generate products, using 'reply' or 'return'.

:(scenario return)
def main [
  1:num, 2:num <- f 34
]
def f [
  12:num <- next-ingredient
  13:num <- add 1, 12:num
  reply 12:num, 13:num
]
+mem: storing 34 in location 1
+mem: storing 35 in location 2

:(before "End Primitive Recipe Declarations")
RETURN,
:(before "End Primitive Recipe Numbers")
put(Recipe_ordinal, "return", RETURN);
put(Recipe_ordinal, "reply", RETURN);  // synonym while teaching
:(before "End Primitive Recipe Checks")
case RETURN: {
  break;  // checks will be performed by a transform below
}
:(before "End Primitive Recipe Implementations")
case RETURN: {
  // Starting Reply
  if (Trace_stream) {
    trace(9999, "trace") << "reply: decrementing callstack depth from " << Trace_stream->callstack_depth << end();
    --Trace_stream->callstack_depth;
    if (Trace_stream->callstack_depth < 0) {
      Current_routine->calls.clear();
      goto stop_running_current_routine;
    }
  }
  Current_routine->calls.pop_front();
  // just in case 'main' returns a value, drop it for now
  if (Current_routine->calls.empty()) goto stop_running_current_routine;
  for (int i = 0; i < SIZE(ingredients); ++i)
    trace(9998, "run") << "result " << i << " is " << to_string(ingredients.at(i)) << end();
  // make reply products available to caller
  copy(ingredients.begin(), ingredients.end(), inserter(products, products.begin()));
  // End Reply
  break;  // continue to process rest of *caller* instruction
}

//: Types in reply instructions are checked ahead of time.

:(before "End Checks")
Transform.push_back(check_types_of_reply_instructions);
:(code)
void check_types_of_reply_instructions(recipe_ordinal r) {
  const recipe& caller = get(Recipe, r);
  trace(9991, "transform") << "--- check types of reply instructions in recipe " << caller.name << end();
  for (int i = 0; i < SIZE(caller.steps); ++i) {
    const instruction& caller_instruction = caller.steps.at(i);
    if (caller_instruction.is_label) continue;
    if (caller_instruction.products.empty()) continue;
    if (caller_instruction.operation < MAX_PRIMITIVE_RECIPES) continue;
    const recipe& callee = get(Recipe, caller_instruction.operation);
    for (int i = 0; i < SIZE(callee.steps); ++i) {
      const instruction& reply_inst = callee.steps.at(i);
      if (reply_inst.operation != RETURN) continue;
      // check types with the caller
      if (SIZE(caller_instruction.products) > SIZE(reply_inst.ingredients)) {
        raise << maybe(caller.name) << "too few values returned from " << callee.name << '\n' << end();
        break;
      }
      for (int i = 0; i < SIZE(caller_instruction.products); ++i) {
        reagent/*copy*/ lhs = reply_inst.ingredients.at(i);
        reagent/*copy*/ rhs = caller_instruction.products.at(i);
        // End Check RETURN Copy(lhs, rhs)
        if (!types_coercible(rhs, lhs)) {
          raise << maybe(callee.name) << reply_inst.name << " ingredient '" << lhs.original_string << "' can't be saved in '" << rhs.original_string << "'\n" << end();
          raise << "  ['" << to_string(lhs.type) << "' vs '" << to_string(rhs.type) << "']\n" << end();
          goto finish_reply_check;
        }
      }
      // check that any reply ingredients with /same-as-ingredient connect up
      // the corresponding ingredient and product in the caller.
      for (int i = 0; i < SIZE(pre { line-height: 125%; }
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<font color="#ffffff" face="helvetica, arial">&nbsp;<br><big><big><strong><a href="ranger.html"><font color="#ffffff">ranger</font></a>.__main__</strong></big></big></font></td
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><font color="#ffffff" face="helvetica, arial"><a href=".">index</a><br><a href="file:/home/hut/ranger/ranger/__main__.py">/home/hut/ranger/ranger/__main__.py</a></font></td></tr></table>
    <p><tt>#&nbsp;coding=utf-8<