//: Calls can take ingredients just like primitives. To access a recipe's
//: ingredients, use 'next-ingredient'.
:(scenario "next_ingredient")
recipe main [
  f 2:literal
]
recipe f [
  12:integer <- next-ingredient
  13:integer <- add 1:literal, 12:integer
]
+run: instruction f/1
+mem: location 12 is 2
+mem: storing 3 in location 13

:(before "End call Fields")
vector<vector<int> > ingredient_atoms;
size_t next_ingredient_to_process;
:(replace{} "call(recipe_number r)")
call(recipe_number r) :running_recipe(r), pc(0), next_ingredient_to_process(0) {}

:(replace "rr.calls.push(call(instructions[pc].operation))" following "End Primitive Recipe Implementations")
call callee(instructions[pc].operation);
for (vector<reagent>::iterator p = instructions[pc].ingredients.begin(); p != instructions[pc].ingredients.end(); ++p) {
  callee.ingredient_atoms.push_back(read_memory(*p));
}
rr.calls.push(callee);

:(before "End Primitive Recipe Declarations")
NEXT_INGREDIENT,
:(before "End Primitive Recipe Numbers")
Recipe_number["next-ingredient"] = NEXT_INGREDIENT;
:(before "End Primitive Recipe Implementations")
case NEXT_INGREDIENT: {
  if (rr.calls.top().next_ingredient_to_process < rr.calls.top().ingredient_atoms.size()) {
    trace("run") << "product 0 is "
        << rr.calls.top().ingredient_atoms[rr.calls.top().next_ingredient_to_process][0];
    write_memory(instructions[pc].products[0],
        rr.calls.top().ingredient_atoms[rr.calls.top().next_ingredient_to_process]);
    ++rr.calls.top().next_ingredient_to_process;
  }
  break;
}