История изменений

Исправление monk, 21.11.13 11:59 (текущая версия) :

только трансформации.

Ну так я и на C++ могу написать

#include <iostream>

enum selector {Lit, Plus, Mult};
struct expr
{
  Selector t;
  expr *value1, *value2;
  int value;
  expr(int val) { t = Lit; value = val; }
  expr(selector _t, expr *_v1, expr *_v2) { t = _t; value1 = _v1; value2 = _v2 };
  string show() 
  { 
     case (t)
     {
        Lit: return "Lit(" + to_string(value) + ")";
        Plus: return "Plus(" + value1.show() + "," +value2.show() + ")";
        Mult: return "Mult(" + value1.show() + "," +value2.show() + ")";
     }
  }
  ~expr() { delete value1; delete value2; }
}

expr* plus(expr *a, expr* b) { new expr(Plus, a, b); }
expr* mult(expr *a, expr* b) { new expr(Mult, a, b); }
int eval(expr *a)
{
   case (a->t)
   {
      Lit: return a->value;
      Plus: return eval(a->value1) + eval(a->value2);
      Mult: return eval(a->value1) * eval(a->value2);
   }
}

int main()
{
   expr *x = new expr(Mult, new expr Plus(1, 2), new expr Plus(3, 4));
   cout << x.show() << end;
   cout << eval(x) << endl;
}

Исправление monk, 21.11.13 11:56:

только трансформации.

Ну так я и на C++ могу написать

#include <iostream>

enum selector {Lit, Plus, Mult};
struct expr
{
  Selector t;
  expr *value1, *value2;
  int value;
  expr(int val) { t = Lit; value = val; }
  expr(selector _t, expr *_v1, expr *_v2) { t = _t; value1 = _v1; value2 = _v2 };
  string show() 
  { 
     case (t)
     {
        Lit: return "Lit (" + to_string(value) + ")";
        Plus: return "Plus (" + value1.show() + "," +value2.show() + ")";
        Mult: return "Mult(" + value1.show() + "," +value2.show() + ")";
     }
  }
  ~expr() { delete value1; delete value2; }
}

expr* plus(expr *a, expr* b) { new expr(Plus, a, b); }
expr* mult(expr *a, expr* b) { new expr(Mult, a, b); }
int eval(expr *a)
{
   case (a->t)
   {
      Lit: return a->value;
      Plus: return eval(a->value1) + eval(a->value2);
      Mult: return eval(a->value1) * eval(a->value2);
   }
}

int main()
{
   expr *x = new expr(Mult, new expr Plus(1, 2), new expr Plus(3, 4));
   cout << x.show() << end;
   cout << eval(x) << endl;
}

Исходная версия monk, 21.11.13 11:56:

только трансформации.

Ну так я и на C++ могу написать

#include <iostream>

enum selector {Lit, Plus, Mult};
struct expr
{
  Selector t;
  expr *value1, *value2;
  int value;
  expr(int val) { t = Lit; value = val; }
  expr(selector _t, expr *_v1, expr *_v2) { t = _t; value1 = _v1; value2 = _v2 };
  string show() 
  { 
     case (t)
     {
        Lit: return "Lit (" + to_string(value) + ")";
        Plus: return "Plus (" + value1.show() + "," +value2.show() + ")";
        Mult: return "Mult(" + value1.show() + "," +value2.show() + ")";
  }
  ~expr() { delete value1; delete value2; }
}

expr* plus(expr *a, expr* b) { new expr(Plus, a, b); }
expr* mult(expr *a, expr* b) { new expr(Mult, a, b); }
int eval(expr *a)
{
   case (a->t)
   {
      Lit: return a->value;
      Plus: return eval(a->value1) + eval(a->value2);
      Mult: return eval(a->value1) * eval(a->value2);
   }
}

int main()
{
   expr *x = new expr(Mult, new expr Plus(1, 2), new expr Plus(3, 4));
   cout << x.show() << end;
   cout << eval(x) << endl;
}