scope test_BStack

/* Goal: Java code with backtracking, like this, to return 4 different values:

  S color = "black" or "white";
  S shape = "circle" or "square";
  return "A " + color + " " + shape;
*/

sclass #OneBranch extends VStackComputableWithStep<S> {
  S color;
  
  void step(VStack stack) {
    cast stack to BStack<?>;

    if (step == 0) {
      step = 1;
      stack.options(this,
        ivf1WithToString("black", f -> f.color = "black"),
        ivf1WithToString("white", f -> f.color = "white"));
    } else
      stack.return("Color is " + color);
  }
}

sclass #TwoBranches extends VStackComputableWithStep<S> {
  S color, shape;

  void step(VStack stack) {
    cast stack to BStack<?>;

    if (step == 0) {
      step = 1;
      print("Creating options at step 0");
      stack.options(this,
        ivf1WithToString("black", f -> f.color = "black"),
        ivf1WithToString("white", f -> f.color = "white"));
    } else if (step == 1) {
      step = 2;
      print("Creating options at step 1");
      stack.options(this,
        ivf1WithToString("circle", f -> f.shape = "circle"),
        ivf1WithToString("square", f -> f.shape = "square"));
    } else
      stack.return("A " + color + " " + shape);
  }
}

svoid test_BStack() {
  test_BStack_oneBranch();
  test_BStack_twoBranches();
}

svoid test_BStack_oneBranch() {
  assertEqualsVerbose(
    ll("Color is black", "Color is white"),
    new BStackComputeAllWithPrintStruct(new OneBranch)!);
}

svoid test_BStack_twoBranches() {
  assertEqualsVerbose(
    ll("A black circle", "A black square",
      "A white circle", "A white square"),
    new BStackComputeAllWithPrintStruct(new TwoBranches)!);
}