path: root/cpp/019array

// Support for arrays.
:(before "End Mu Types")
// We'll use this array as a running example:
int integer_array = Type_number["integer-array"] = Next_type_number++;
Type[integer_array].is_array = true;
Type[integer_array].element.push_back(integer);

:(scenario copy_array)
# Arrays can be copied around with a single instruction just like integers,
# no matter how large they are.
recipe main [
  1:integer <- copy 3:literal
  2:integer <- copy 14:literal
  3:integer <- copy 15:literal
  4:integer <- copy 16:literal
  5:integer-array <- copy 1:integer-array
]
+run: instruction main/4
+run: ingredient 0 is 1
+mem: location 1 is 3
+mem: location 2 is 14
+mem: location 3 is 15
+mem: location 4 is 16
+mem: storing in location 5
+mem: storing in location 6
+mem: storing in location 7
+mem: storing in location 8

:(replace{} "size_t size_of(reagent r)")
size_t size_of(reagent r) {
  type_info t = Type[r.types[0]];
  if (t.is_record) {
    int result = 0;
    for (size_t i = 0; i < t.size; ++i) {
      ostringstream out;
      out << result;
      reagent x(out.str());
      copy(t.elements[i].begin(), t.elements[i].end(), inserter(x.types, x.types.begin()));
      result += size_of(x);
    }
    return result;
  }
  if (t.is_array) {
    assert(!r.name.empty());
    int base = to_int(r.name);
    if (Memory[base] == 0) return 0;
    ostringstream out;
    out << base+1;
    reagent x(out.str());
    x.types.push_back(t.element[0]);
    return 1 + Memory[base]*size_of(x);
  }
  // scalar
  return t.size;
}

:(before "End Globals")
// Operator to look at elements of arrays.
const int INDEX = 20;
:(before "End Primitive Recipe Numbers")
Recipe_number["index"] = INDEX;
Next_recipe_number++;
:(before "End Primitive Recipe Implementations")
case INDEX: {
  trace("run") << "ingredient 0 is " << instructions[pc].ingredients[0].name;
  reagent base = canonize(instructions[pc].ingredients[0]);
  int base_address = to_int(base.name);
  int base_type = base.types[0];
  assert(Type[base_type].is_array);
  trace("run") << "ingredient 1 is " << instructions[pc].ingredients[1].name;
  size_t offset = to_int(instructions[pc].ingredients[1].name);
  int src = base_address + 1 + offset*size_of(reagent(Type[base_type].element[0]));
  trace("run") << "address to copy is " << src;
  int src_type = Type[base_type].element[0];
  trace("run") << "its type is " << src_type;
  ostringstream s;
  s << src;
  reagent tmp(s.str());
  tmp.types.push_back(src_type);
  vector<int> result(read_memory(tmp));
  trace("run") << "product 0 is " << result[0];
  write_memory(instructions[pc].products[0], result);
  break;
}

:(scenario "index")
recipe main [
  1:integer <- copy 3:literal
  2:integer <- copy 14:literal
  3:integer <- copy 15:literal
  4:integer <- copy 16:literal
  5:integer <- index 1:integer-array, 0:literal
]
+run: instruction main/4
+run: ingredient 0 is 1
+run: ingredient 1 is 0
+run: address to copy is 2
+run: its type is 1
+mem: location 2 is 14
+run: product 0 is 14
+mem: storing in location 5

:(before "End Globals")
// To write to fields of records, you need their address.
const int INDEX_ADDRESS = 21;
:(before "End Primitive Recipe Numbers")
Recipe_number["index-address"] = INDEX_ADDRESS;
Next_recipe_number++;
:(before "End Primitive Recipe Implementations")
case INDEX_ADDRESS: {
  trace("run") << "ingredient 0 is " << instructions[pc].ingredients[0].name;
  reagent base = canonize(instructions[pc].ingredients[0]);
  int base_address = to_int(base.name);
  int base_type = base.types[0];
  assert(Type[base_type].is_array);
  trace("run") << "ingredient 1 is " << instructions[pc].ingredients[1].name;
  size_t offset = to_int(instructions[pc].ingredients[1].name);
  int src = base_address + 1 + offset*size_of(reagent(Type[base_type].element[0]));
  trace("run") << "address to copy is " << src;
  vector<int> result;
  result.push_back(src);
  trace("run") << "product 0 is " << result[0];
  write_memory(instructions[pc].products[0], result);
  break;
}

:(scenario "index_address")
recipe main [
  1:integer <- copy 3:literal
  2:integer <- copy 14:literal
  3:integer <- copy 15:literal
  4:integer <- copy 16:literal
  5:integer <- index-address 1:integer-array, 0:literal
]
+run: instruction main/4
+run: ingredient 0 is 1
+run: ingredient 1 is 0
+run: address to copy is 2
+mem: storing in location 5