C++ if with initializer

Table of contents

const int Pen{10};
const int Marker{20};
const int Eraser{30};
const int Rectangle{40};
const int Circle{50};
const int Ellipse{60};

int main([[maybe_unused]] int argc, [[maybe_unused]] char **argv) {
  bool go{false};
  // initialized inplace. Only one variable is allowed
  if (int high_speed{33}; go) {
    // high_speed is visible at if
    if (high_speed > 5) {
      cout << "Slow down" << endl;
    } else {
      cout << "All good!" << endl;
    }
  } else {
    // high_speed is visible at else
    cout << "high_speed: " << high_speed << endl;
    cout << "Stop" << endl;
  }

  // not visible outside block
  // cout << "high_speed: " << high_speed << endl;

  int tool{Eraser};
  // switch accept ONE initializer like if
  switch (double strength{3.56}; tool) {
    case Pen: {
      std::cout << "Active tool is Pen. strength : " << strength << std::endl;
    } break;

    case Marker: {
      std::cout << "Active tool is Marker. strength : " << strength
                << std::endl;
    } break;

    case Eraser:
    case Rectangle:
    case Circle: {
      std::cout << "Drawing Shapes. strength : " << strength << std::endl;
    } break;

    case Ellipse: {
      std::cout << "Active tool is Ellipse. strength : " << strength
                << std::endl;
    } break;

    default: {
      std::cout << "No match found. strength : " << strength << std::endl;
    } break;
  }

  return 0;
}

Possible output

high_speed: 33
Stop
Drawing Shapes. strength : 3.56

References

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