// lem.cxx
// Written by Michael Main, mostly to show how to use functions.

#include <iostream>
#include <cstdlib>
#include <iomanip>
using namespace std;

const double AG = -9.8/6;  // Acceleration from lunar gravity m/sec^2
const double AT = 10.0;    // Thrust upward in m/sec^2;
const double DELTA = 0.1;  // How much time passes each iteration

// FUNCTION PROTOTYPES

double calc_height(double height, double velocity);
// The value calculated by this function is the new height of the
// lander after DELTA seconds have passed.  The two parameters are
// the height and velocity of the lander just before the time passed.


int main( )
{
    double height;    // Height in meters above lunar surface
    double velocity;  // Current velocity m/sec (negative is down)
    bool is_thrust;   // True if the thruster is on

    // Get the initial data
    cout << "The Lunar Lander program" << endl;
    cout << "Type the initial height (m) and velocity (m/sec): ";
    cin >> height >> velocity;
    is_thrust = false;
    
    // Print a heading:
    cout << "    HEIGHT  VELOCITY T" << endl;
    
    while (height > 0)
    {
        // Update the variables to reflect the passage of time
        new_height = calc_height(height, velocity);
	
	// Print the current variable values
	cout << setw(10) << height;
	cout << setw(10) << velocity;
	cout << setw(2) << is_thrust << endl;
    }

    return EXIT_SUCCESS;
}


double calc_height(double height, double velocity)
{
    return (height + velocity * DELTA);
}