College C++ problem...

[TrazPFloyd]

Hello guys,

I'm having a tricky assignment this week in C++, I have completed it and I'm wondering if the code is correct or not. Anyway here is the problem, bear with me this is extensive:

The distance to a landing point of a projectile, launched at an angle ang (in radians) with an initial velocity of vel (in feet per second), ignoring air resistance, is given by the formula

Distance= (vel 2 * sin(2*ang))/32.2

Write a C++ program that implements a game in which the user first enters the distance to a target. The user then enters the angle and velocity for launching a projectile. If the projectile comes within 0.1% of the distance to the target, the user wins the game. If the projectile doesn’t come close enough, the user is told how far off the projectile is and is allowed to try again. If there isn’t a winning input after five tries, the user loses the game.

To simply the input for the user, your program should allow the angle to be entered in degrees. The formula for converting degrees to radians is

Radians=(degrees*3.14159)/180

Each of the formulas in this problem must be implemented as a C++ value returning free function. Your program should prompt the user for input appropriately and label the output values.

NOTE: A function to calculate the sin of an angle in radians is in the include file math.h.

Okay now that you have seen the assignment, here is my program's source code:

#include <iostream.h>
#include <math.h>

//	Declare objects in global scope to be used by all functions, vel (velocity) ang (degress)
//	and total to hold calculation of distance being less than or greater than 0.1
double vel, ang, total;

//	Constructor for function playGame
void playGame(double uDistance);

//	Constructor for function convertRadians
double convertRadians(double& radians);

//  Constructor for function calculateDistance
double calculateDistance(double uDistance);

//	Begin program with main() statement of void type
void main()
{

	//	Declare a uDistance variable for user defined distance
	double uDistance;
	char prompt;

	//	Do the following steps
	do
	{

		//	Introduce user to program
		cout << "************* Projectile Game *************" << endl;
		cout << "Welcome to the projectile game!  Please enter a distance--";

		//	Get input from user for uDistance
		cin >> uDistance;


		//	Play the game, use function playGame
		playGame(uDistance);


		// Ask user if they would want to play again
		cout << "Would you like to play again? Enter Y for yes, any other character otherwise." << endl;
		cin >> prompt;

		cout << endl;
		cout << endl;
	}
	while (prompt == 'Y' || prompt == 'y');

	cin.get();
}

void playGame(double uDistance)
{
	//  Begin for
	for (int tries = 1; tries <= 5; tries++)
	{
		//	Ask user for angle input
		cout << "Please enter an angle--";
		cin >> ang;

		//	Convert angle value to radians
		convertRadians(ang);

		cout << "Please enter a velocity--";
		cin >> vel;

		//	Call upon calculateDistance to find if user wins or not
		calculateDistance(uDistance);

		if (total <= 0.1)
		{
			cout << "You won the game!" << endl;
			cout << "You came within " << total << " of the target! Congratulations!" << endl;
			break; // Break out of the for loop
		}
		else
		{
			cout << "You didn't win the game, please try again." << endl;
			cout << "You came within " << total << " of the target." << endl;
			cout << endl;
		}

		// End if
	}

	// End for

}

double convertRadians(double& radians)
{
	radians = ((ang*3.14159)/180);

	return radians;
}

double calculateDistance(double uDistance)
{
	double distance;
	double sinTotal = (2 * ang);
	distance = (((vel*vel) * sin(sinTotal)/32.2));
	total = distance/uDistance;

	return total;
}

My main question is, is this correct?

I'm having some trouble getting ahold of the professor to check this out with him.

If I'm not correct, am I on track? I get really really strange output for some of my distance/angle/velocity combinations.

Thank you for your assistance.

Traz

[SilentStrike]

Couple suggestions.

1. Get rid of the global variables. Use the return values rather than directly using the global. Rather than

calculateDistance(uDistance); // modifies global total

if (total <= 0.1) // etc

Make a local variable total inside that block.

double total = calculateDistance(uDistance);

if (total <= 0.1)

2. Your calculateDistance function is actually returning a ratio... it's not doing what it's advertising.

3. Don't use void main.

http://homepages.tesco.net/~J.deBoyn...void-main.html

[TrazPFloyd]

Hello,

Thank you very much for looking over my program. Implementing total as a local variable makes sense. I've also done int main() as everyone recommends to do that here (hard to break habit lol)

Having said that I'm trying to understand what you mean by what you stated in #2. You stated that the function was returning a ratio. Do you mean distance/uDistance?

I'm attempting to fulfill the following requirement:

the user first enters the distance to a target.... If the projectile comes within 0.1% of the distance to the target, the user wins the game. If the projectile doesn’t come close enough, the user is told how far off the projectile is and is allowed to try again.

I have set the user's input for distance as uDistance. How can I calculate when the projectile comes within .1% of the distance to the target? distance/uDistance right?

Thank you very much again for your help, its very very appreciated.

Traz

[SilentStrike]

This is what you need for less than .1% error.

if (abs(1.0 - distance/uDistance) < .001) { // user entered good enough values