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

:(code)
void run(string form) {
  run(add_recipe(form));
}

void run(recipe_number r) {
  vector<instruction>& instructions(Recipe[r].steps);
  int n = 0;
  vector<instruction>::iterator p;
  for (n = 0, p = instructions.begin(); p != instructions.end(); ++p, ++n) {
    trace("run") << "instruction " << n;
    switch (p->operation) {
    case 1: {  // copy
      vector<int> data = read_memory(p->ingredients[0]);
      trace("run") << "ingredient 0 is " << data[0];
      write_memory(p->products[0], data);
      break;
    }
    default:
      raise << "undefined operation " << p->operation;
    }
  }
}

vector<int> read_memory(reagent x) {
  vector<int> result;
  result.push_back(to_int(x.name));
  return result;
}

void write_memory(reagent x, vector<int> data) {
  int dest = to_int(x.name);
  trace("mem") << "storing in location " << dest;
  Memory[dest] = data[0];
}

int to_int(string n) {
  char* end = NULL;
  int result = strtol(n.c_str(), &end, /*any base*/0);
  assert(*end == '\0');
  return result;
}