!752

!include #1004863 // Dynamic Concepts

sclass CKnownString extends Concept {
  S s;
  
  *() {}
  *(S *s) {}
}

sclass CUnknownString extends Concept {}

sclass CUnknownCharacter extends Concept {}

sclass CKnownCharacter extends Concept {
  char c;
  
  *() {}
  *(char *c) {}
}

sclass CharInString extends Concept {
  new Ref string;
  int index;
  
  *() {}
  *(Concept string, int *index) { this.string.set(string); }
}

sclass CUnknownInt extends Concept {}

sclass CKnownInt extends Concept {
  BigInteger value;
  
  *() {}
  *(int value) { this.value = bigint(value); }
}

sclass CKnownEquals extends Concept {
  new RefL what;
}

sclass Question extends Concept {}

sclass WhichCharacterIsIt extends Question {
  new Ref character;
  new Ref answer;
  
  *() {}
  *(Concept character) { this.character.set(character); }
}

p {
  CKnownString s = new CKnownString("hello world");
  CharInString c = new CharInString(s, 3);
  WhichCharacterIsIt question = new WhichCharacterIsIt(c);
  tryToAnswer(question);
}

svoid tryToAnswer(WhichCharacterIsIt question) {
  // We need a rewriting engine here
}