:(scenarios run)
:(scenario copy_literal)
recipe main [
  1:integer <- copy 23:literal
]
+run: instruction main/0
+run: ingredient 0 is 23
+mem: storing 23 in location 1

:(scenario copy)
recipe main [
  1:integer <- copy 23:literal
  2:integer <- copy 1:integer
]
+run: instruction main/1
+run: ingredient 0 is 1
+mem: location 1 is 23
+mem: storing 23 in location 2

:(before "End Types")
// Book-keeping while running a recipe.
//: Later layers will change this.
struct routine {
  recipe_number running_recipe;
  size_t running_at;
  routine(recipe_number r) :running_recipe(r), running_at(0) {}
};

:(before "End Globals")
routine Current_routine(0);

:(code)
void run(recipe_number r) {
  run(routine(r));
}

void run(routine rr) {
  Current_routine = rr;
  while (!done(rr)) {
    vector<instruction>& instructions = steps(rr);
    size_t& pc = running_at(rr);
    // Running one instruction.
    if (instructions[pc].is_label) { ++pc; continue; }
    trace("run") << "instruction " << recipe_name(rr) << '/' << pc;
//?     cout << instructions[pc].operation << '\n'; //? 1
    switch (instructions[pc].operation) {
      // Primitive Recipe Implementations.
      case COPY: {
        trace("run") << "ingredient 0 is " << instructions[pc].ingredients[0].name;
        vector<int> data = read_memory(instructions[pc].ingredients[0]);
        write_memory(instructions[pc].products[0], data);
        break;
      }
      // End Primitive Recipe Implementations.
      default: {
        cout << "not a primitive op: " << instructions[pc].operation << '\n';
      }
    }
    ++pc;
  }
}

//: Some helpers.
//: We'll need to override these later as we change the definition of routine.
//: Important that they return referrences into the routine.
inline size_t& running_at(routine& rr) {
  return rr.running_at;
}

inline string recipe_name(routine& rr) {
  return Recipe[rr.running_recipe].name;
}

inline vector<instruction>& steps(routine& rr) {
  return Recipe[rr.running_recipe].steps;
}

inline bool done(routine& rr) {
  return running_at(rr) >= steps(rr).size();
}

:(before "End Main")
if (argc > 1) {
  setup();
  for (int i = 1; i < argc; ++i) {
    ifstream fin(argv[i]);
    while (!fin.eof()) add_recipe(fin);
    fin.close();
  }

  recipe_number r = Recipe_number[string("main")];
  if (r) run(r);
  dump_memory();
}

//: helper for tests

:(before "End Globals")
// track recipes added so that we can cleanup after each test
vector<recipe_number> recipes_added_by_test;

:(code)
void run(string form) {
  vector<recipe_number> tmp = add_recipes(form);
  recipes_added_by_test.insert(recipes_added_by_test.end(), tmp.begin(), tmp.end());
  transform_all();
  run(recipes_added_by_test.front());
}

:(before "End Setup")
for (size_t i = 0; i < recipes_added_by_test.size(); ++i) {
  Recipe_number.erase(Recipe[recipes_added_by_test[i]].name);
  Recipe.erase(recipes_added_by_test[i]);
}
recipes_added_by_test.clear();

:(code)
//: beware: overridden in later layers
vector<int> read_memory(reagent x) {
//?   cout << "read_memory: " << x.to_string() << '\n'; //? 1
  vector<int> result;
  if (x.types[0] == 0) {  // literal
    result.push_back(x.value);
    return result;
  }
  int base = x.value;
  for (size_t offset = 0; offset < Type[x.types[0]].size; ++offset) {
    int val = Memory[base+offset];
    trace("mem") << "location " << base+offset << " is " << val;
    result.push_back(val);
  }
  return result;
}

//: beware: overridden in later layers
void write_memory(reagent x, vector<int> data) {
  if (is_dummy(x)) return;
  int base = x.value;
  size_t size = size_of(x);
  if (size != data.size()) raise << "size mismatch in storing to " << x.to_string();
  for (size_t offset = 0; offset < size; ++offset) {
    trace("mem") << "storing " << data[offset] << " in location " << base+offset;
    Memory[base+offset] = data[offset];
  }
}

:(code)
size_t size_of(const reagent& r) {
  type_info t = Type[r.types[0]];
  if (!t.is_record && !t.is_array) return t.size;
  // End size_of Cases.
  return t.size;
}

bool is_dummy(const reagent& x) {
  return x.name == "_";
}

:(scenario run_label)
recipe main [
  +foo
  1:integer <- copy 23:literal
  2:integer <- copy 1:integer
]
+run: instruction main/1
+run: instruction main/2
-run: instruction main/0

:(scenario run_dummy)
recipe main [
  _ <- copy 0:literal
]
+run: instruction main/0