#include <iostream>

// Consider the following piecewise-defined function:
//
//                  /   0,              x <= -1,
//                  |
//                  |  -1,         -1 < x < 0,
//                  |
//     square(x) = <    0,               x = 0,
//                  |
//                  |   1,          0 < x < 1,
//                  |
//                  \   0,               x >= 1.
//
// Its graph looks like:
//
//
//                          |
//                        1 o-------o
//                          |
//                          |
//     --------------o------o------o-------------- x
//                  -1      0      1
//                  o-------o -1
//                          |
//
//
// The open circles indicate that the corresponding
// endpoint is not included, while the closed circles
// indicate that the endpoint is included.
//
// For example:
//
//     x = -2.0    ->    square(x) =  0
//     x = -1.0    ->    square(x) =  0
//     x = -0.4    ->    square(x) = -1
//     x =  0.0    ->    square(x) =  0
//     x =  0.6    ->    square(x) =  1
//     x =  1.0    ->    square(x) =  0
//     x =  3.2    ->    square(x) =  0
//
// The following program attempts to implement this
// function using a cascading conditional statement.
//
// It compiles, but it does not always produce the
// correct result.
//
// Determine what is wrong and fix the program.

// Function declarations
int main();

// Function definitions
int main() {
    double x{};

    std::cout << "Enter a number 'x': ";
    std::cin >> x;

    ///////////////////////////////////////////
   // Exercise: This does not work. Fix it. //
  ///////////////////////////////////////////

    if ( x < -1.0 ) {
        std::cout << "square(x) = " << 0.0 << std::endl;
    } else if ( x < 0.0 ) {
        std::cout << "square(x) = " << -1.0 << std::endl;
    } else if ( x > 0.0 ) {
        std::cout << "square(x) = " << 1.0 << std::endl;
    } else if ( x > 1.0 ) {
        std::cout << "square(x) = " << 0.0 << std::endl;
    } else {
        std::cout << "square(x) = " << 0.0 << std::endl;
    }

    return 0;
}









































// Hint:
//
// Test the program using values from each of the five
// cases in the definition.
//
// In particular, test the boundary values:
//
//     x = -1
//     x =  0
//     x =  1
//
// Also test values strictly between and outside these
// boundaries.
//
// For each condition, ask:
//
//     If this condition is false, what do I already
//     know about 'x' when I reach the next condition?









































// One problem occurs here:
//
//     } else if ( x > 0.0 ) {
//
// This condition includes every positive value of 'x',
// including values greater than or equal to 1.
//
// Consequently, if x = 2, this condition is true and
// the program prints 1. The later test
//
//     } else if ( x > 1.0 ) {
//
// can therefore never be reached when its condition
// would be true.
//
// A cascading conditional must be arranged so that
// each branch correctly eliminates values before the
// next branch is considered.









































// Here is one solution:

/*
int main() {
    double x{};

    std::cout << "Enter a number 'x': ";
    std::cin >> x;

    if ( x <= -1.0 ) {
        // Here, x <= -1.

        std::cout << "square(x) = " << 0.0 << std::endl;
    } else if ( x < 0.0 ) {
        // The first condition was false, so x > -1.
        // Thus, we now know
        //
        //     -1 < x < 0.

        std::cout << "square(x) = " << -1.0 << std::endl;
    } else if ( x == 0.0 ) {
        // The first two conditions were false and
        // this condition tells us x = 0.

        std::cout << "square(x) = " << 0.0 << std::endl;
    } else if ( x < 1.0 ) {
        // We already know that x > 0. Together with
        // the current condition, this gives
        //
        //     0 < x < 1.

        std::cout << "square(x) = " << 1.0 << std::endl;
    } else {
        // All previous conditions were false, so
        //
        //     x >= 1.

        std::cout << "square(x) = " << 0.0 << std::endl;
    }

    return 0;
}
*/