:(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

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

:(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) {
    // Primitive Recipe Implementations.
    case 1: {  // copy
      trace("run") << "ingredient 0 is " << p->ingredients[0].name;
      vector<int> data = read_memory(p->ingredients[0]);
      write_memory(p->products[0], data);
      break;
    }
    // End Primitive Recipe Implementations.
    default:
      raise << "undefined operation " << p->operation;
    }
  }
}

vector<int> read_memory(reagent x) {
  vector<int> result;
  if (x.types[0] == 0) {  // literal
    result.push_back(to_int(x.name));
    return result;
  }
  int val = Memory[to_int(x.name)];
  trace("mem") << "location " << x.name << " is " << val;
  result.push_back(val);
  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];
}

:(before "End Primitive Recipe Numbers")
// Arithmetic ops.
Recipe_number["add"] = 2;
Next_recipe_number++;
Recipe_number["subtract"] = 3;
Next_recipe_number++;
Recipe_number["multiply"] = 4;
Next_recipe_number++;
Recipe_number["divide"] = 5;
Next_recipe_number++;
Recipe_number["divide_with_remainder"] = 6;
Next_recipe_number++;
:(before "End Primitive Recipe Implementations")
  case 2: {  // add
    trace("run") << "ingredient 0 is " << p->ingredients[0].name;
    vector<int> arg0 = read_memory(p->ingredients[0]);
    assert(arg0.size() == 1);
    trace("run") << "ingredient 1 is " << p->ingredients[1].name;
    vector<int> arg1 = read_memory(p->ingredients[1]);
    assert(arg1.size() == 1);
    vector<int> result;
    result.push_back(arg0[0]+arg1[0]);
    trace("run") << "product 0 is " << result[0];
    write_memory(p->products[0], result);
    break;
  }
  case 3: {  // subtract
    trace("run") << "ingredient 0 is " << p->ingredients[0].name;
    vector<int> arg0 = read_memory(p->ingredients[0]);
    assert(arg0.size() == 1);
    trace("run") << "ingredient 1 is " << p->ingredients[1].name;
    vector<int> arg1 = read_memory(p->ingredients[1]);
    assert(arg1.size() == 1);
    vector<int> result;
    result.push_back(arg0[0]-arg1[0]);
    trace("run") << "product 0 is " << result[0];
    write_memory(p->products[0], result);
    break;
  }
  case 4: {  // multiply
    trace("run") << "ingredient 0 is " << p->ingredients[0].name;
    vector<int> arg0 = read_memory(p->ingredients[0]);
    assert(arg0.size() == 1);
    trace("run") << "ingredient 1 is " << p->ingredients[1].name;
    vector<int> arg1 = read_memory(p->ingredients[1]);
    assert(arg1.size() == 1);
    trace("run") << "ingredient 1 is " << arg1[0];
    vector<int> result;
    result.push_back(arg0[0]*arg1[0]);
    trace("run") << "product 0 is " << result[0];
    write_memory(p->products[0], result);
    break;
  }
  case 5: {  // divide
    trace("run") << "ingredient 0 is " << p->ingredients[0].name;
    vector<int> arg0 = read_memory(p->ingredients[0]);
    assert(arg0.size() == 1);
    trace("run") << "ingredient 1 is " << p->ingredients[1].name;
    vector<int> arg1 = read_memory(p->ingredients[1]);
    assert(arg1.size() == 1);
    trace("run") << "ingredient 1 is " << arg1[0];
    vector<int> result;
    result.push_back(arg0[0]/arg1[0]);
    trace("run") << "product 0 is " << result[0];
    write_memory(p->products[0], result);
    break;
  }
  case 6: {  // divide_with_remainder
    trace("run") << "ingredient 0 is " << p->ingredients[0].name;
    vector<int> arg0 = read_memory(p->ingredients[0]);
    assert(arg0.size() == 1);
    trace("run") << "ingredient 1 is " << p->ingredients[1].name;
    vector<int> arg1 = read_memory(p->ingredients[1]);
    assert(arg1.size() == 1);
    vector<int> result0;
    result0.push_back(arg0[0]/arg1[0]);
    trace("run") << "product 0 is " << result0[0];
    write_memory(p->products[0], result0);
    vector<int> result1;
    result1.push_back(arg0[0]%arg1[0]);
    trace("run") << "product 1 is " << result1[0];
    write_memory(p->products[1], result1);
    break;
  }
:(scenario "add_literal")
recipe main [
  1:integer <- add 23:literal, 34:literal
]
+run: instruction 0
+run: ingredient 0 is 23
+run: ingredient 1 is 34
+run: product 0 is 57
+mem: storing in location 1
:(scenario "add")
recipe main [
  1:integer <- copy 23:literal
  2:integer <- copy 34:literal
  3:integer <- add 1:integer, 2:integer
]
+run: instruction 2
+run: ingredient 0 is 1
+mem: location 1 is 23
+run: ingredient 1 is 2
+mem: location 2 is 34
+run: product 0 is 57
+mem: storing in location 3
:(scenario "subtract_literal")
recipe main [
  1:integer <- subtract 5:literal, 2:literal
]
+run: instruction 0
+run: ingredient 0 is 5
+run: ingredient 1 is 2
+run: product 0 is 3
+mem: storing in location 1
:(scenario "subtract")
recipe main [
  1:integer <- copy 23:literal
  2:integer <- copy 34:literal
  3:integer <- subtract 1:integer, 2:integer
]
+run: instruction 2
+run: ingredient 0 is 1
+mem: location 1 is 23
+run: ingredient 1 is 2
+mem: location 2 is 34
+run: product 0 is -11
+mem: storing in location 3
:(scenario "multiply_literal")
recipe main [
  1:integer <- multiply 2:literal, 3:literal
]
+run: instruction 0
+run: ingredient 0 is 2
+run: ingredient 1 is 3
+run: product 0 is 6
+mem: storing in location 1
:(scenario "multiply")
recipe main [
  1:integer <- copy 4:literal
  2:integer <- copy 6:literal
  3:integer <- multiply 1:integer, 2:integer
]
+run: instruction 2
+run: ingredient 0 is 1
+mem: location 1 is 4
+run: ingredient 1 is 2
+mem: location 2 is 6
+run: product 0 is 24
+mem: storing in location 3
:(scenario "divide_literal")
recipe main [
  1:integer <- divide 8:literal, 2:literal
]
+run: instruction 0
+run: ingredient 0 is 8
+run: ingredient 1 is 2
+run: product 0 is 4
+mem: storing in location 1
:(scenario "divide")
recipe main [
  1:integer <- copy 27:literal
  2:integer <- copy 3:literal
  3:integer <- divide 1:integer, 2:integer
]
+run: instruction 2
+run: ingredient 0 is 1
+mem: location 1 is 27
+run: ingredient 1 is 2
+mem: location 2 is 3
+run: product 0 is 9
+mem: storing in location 3
:(scenario "divide_with_remainder_literal")
recipe main [
  1:integer, 2:integer <- divide_with_remainder 9:literal, 2:literal
]
+run: instruction 0
+run: ingredient 0 is 9
+run: ingredient 1 is 2
+run: product 0 is 4
+mem: storing in location 1
+run: product 1 is 1
+mem: storing in location 2
:(scenario "divide_with_remainder")
recipe main [
  1:integer <- copy 27:literal
  2:integer <- copy 11:literal
  3:integer, 4:integer <- divide_with_remainder 1:integer, 2:integer
]
+run: instruction 2
+run: ingredient 0 is 1
+mem: location 1 is 27
+run: ingredient 1 is 2
+mem: location 2 is 11
+run: product 0 is 2
+mem: storing in location 3
+run: product 1 is 5
+mem: storing in location 4

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