#include <iostream>

struct Box
{
    double width;
    double length;
    double height;
};

bool isValidBox(Box b);
double surface(Box b);

int main()
{
    Box box1 = { 2.0, 3.0, 4.0 };
    Box box2 = { 0.0, -2.0, 5.0 };
    Box box3 = { 7.0, 3.0, 4.0 };
    std::cout << "isValidBox( { 2, 3, 4 } ) = "  << std::boolalpha << isValidBox( box1 )  << "\n";
    std::cout << "isValidBox( { 0, -2, 5 } ) = " << std::boolalpha << isValidBox( box2 ) << "\n";
    std::cout << "isValidBox( { 7, 3, 4 } ) = "  << std::boolalpha << isValidBox( box3 )  << "\n";

    std::cout << "surface( { 3, 5, 9 } ) = "  << surface( box1 )  << "\n";
    std::cout << "surface( { 1, 12, 3 } ) = " << surface( box2 ) << "\n";
    std::cout << "surface( { 1, 2, 3 } ) = "  << surface( box3 )  << "\n";

    return 0;
}

//----------------------------------------------------------------------------
// @description check whether the box is a valid box
// @param b a box
// @return true if the box is valid, false otherwise
// @contract isValidBox : Box -> boolean
// @example isValidBox( {3, 5, 9 } ) = true
// @example isValidBox( {0, -2, 3 } ) = false
// @example isValidBox( {1, 2, 3 } ) = true
//----------------------------------------------------------------------------
bool isValidBox(Box b)
{
    return (b.width > 0) &&
           (b.length > 0) &&
           (b.height > 0);
}

//----------------------------------------------------------------------------
// @description calculate the area of the outside surface of a box
// @param b a box
// @return the area of the outside surface of a box
// @contract surface : Box -> double
// @example surface( {3, 5, 9 } ) = 15*2 + 45*2 + 27*2 = 174
// @example surface( {1, 12, 3 } ) = 12*2 + 36*2 + 3*2 = 82
// @example surface( {1, 2, 3 } ) = 2*2 + 6*2 + 3*2 = 22
//----------------------------------------------------------------------------
double surface(Box b)
{
    return ( (b.width * b.length) +
             (b.length * b.height) +
             (b.height * b.width) ) * 2;
}