mu/cpp/literate/010vm

// A mu program is a book of recipes (functions)

:(after "Types")
typedef int recipe_number;
:(before "End Globals")
unordered_map<string, recipe_number> Recipe_number;
unordered_map<recipe_number, recipe> Recipe;
int Next_recipe_number = 1;

:(before "End Types")
// Recipes are lists of instructions. Recipes are 'run' by running their
// instructions.
struct recipe {
  vector<instruction> step;
};

const int idle = 0;  // always the first entry in the recipe book

:(before "struct recipe")
// Each instruction is either of the form:
//   product1, product2, product3, ... <- operation ingredient1, ingredient2, ingredient3, ...
// or just a single 'label' followed by a colon
//   label:
struct instruction {
  bool is_label;
  string label;  // only if is_label
  recipe_number operation;  // only if !is_label
  vector<reagent> ingredients;  // only if !is_label
  vector<reagent> products;  // only if !is_label
  instruction();
  void clear();
};

:(before "struct instruction")
// Ingredients and products all the same kind of 'thing' -- a reagent.
// Reagents refer either to numbers or to locations in memory along with
// 'type' tags telling us how to interpret them. They also can contain
// arbitrary other lists of properties besides types, but we're getting ahead
// of ourselves.
struct reagent {
  string name;
  vector<type_number> types;
  vector<pair<string, property> > properties;
  reagent(string s);
  string to_string();
};

:(before "struct reagent")
struct property {
  vector<string> values;
};

:(before "End Globals")
// Locations refer to a common 'memory'. Each location can store a number.
unordered_map<int, int> Memory;

:(after "Types")
// Types encode how the numbers stored in different parts of memory are
// interpreted. A location tagged as a 'character' type will interpret the
// number 97 as the letter 'a', while a different location of type 'integer'
// would not.
//
// Unlike most computers today, mu stores types in a single big table, shared
// by all the mu programs on the computer. This is useful in providing a
// seamless experience to help understand arbitrary mu programs.
typedef int type_number;
:(before "End Globals")
unordered_map<string, type_number> Type_number;
unordered_map<type_number, type_info> Type;
int Next_type_number = 1;

:(before "End Types")
// You can construct arbitrary new types. Types are either 'records', containing
// 'fields' of other types, 'array's of a single type repeated over and over,
// or 'addresses' pointing at a location elsewhere in memory.
struct type_info {
  int size;
  bool is_address;
  bool is_record;
  bool is_array;
  vector<type_number> target;  // only if is_address
  vector<vector<type_number> > elements;  // only if is_record or is_array
  type_info() :size(0) {}
};



:(code)
// Helpers
  instruction::instruction() :is_label(false), operation(idle) {}
  void instruction::clear() { is_label=false; label.clear(); operation=idle; ingredients.clear(); products.clear(); }

  reagent::reagent(string s) {
    istringstream in(s);
    name = slurp_until(in, ':');
    types.push_back(Type_number[slurp_until(in, '/')]);  // todo: multiple types
  }
  string reagent::to_string() {
    ostringstream out;
    out << "{name: \"" << name << "\", type: " << types[0] << "}";  // todo: properties
    return out.str();
  }

string slurp_until(istream& in, char delim) {
  ostringstream out;
  char c;
  while (in >> c) {
    if (c == delim) {
      break;
    }
    out << c;
  }
  return out.str();
}