My first C++ project!

maths.cpp

/* Adam
 10-3-18
 Basic Math
 Does some maths! */

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

using namespace std;

string prompt(string type)
{

	/*

	  _____                           _
	 |  __ \                         | |
	 | |__) | __ ___  _ __ ___  _ __ | |_
	 |  ___/ '__/ _ \| '_ ` _ \| '_ \| __|
	 | |   | | | (_) | | | | | | |_) | |_
	 |_|   |_|  \___/|_| |_| |_| .__/ \__|
			 | |
			 |_|

	Here I made a function that returns the
	users input as well as prompts them for
	it.

	*/


	string returned; // Initilize variable

	// Logic for this function, I was going to use switch but then it said it expected an int, and I didn't want to make it confusing.

	if (type == "company") {
		cout << "Enter company name: "; // Prompt the user
	}
	if (type == "method") {
		cout << "Enter a payment method (cash, finance): "; // Prompt the user
	}
	if (type == "inDoors") {
		cout << "Enter number of interior doors: "; // Prompt the user
	}
	if (type == "exDoors") {
		cout << "Enter number of exterior doors: "; // Prompt the user
	}
	if (type == "custom") {
		cout << "Set custom sales tax, discount percent, finance charge, and cost of each type of door? (y,n): "; // Prompt the user
	}
	if (type == "tax") {
		cout << "Enter the tax as a decimal. For example, .075 would be 7.5%: "; // Prompt the user
	}
	if (type == "discount") {
		cout << "Enter the discount percent (for using cash, won't matter otherwise) as a decimal. For example, .1 would be 10%: "; // Prompt the user
	}
	if (type == "charge") {
		cout << "Enter the finance charge (for using finance instead of cash) as a decimal. For example, .15 would be 15%: "; // Prompt the user
	}
	if (type == "inPrice") {
		cout << "Enter price of an interior door: "; // Prompt the user
	}
	if (type == "exPrice") {
		cout << "Enter price of an exterior door: "; // Prompt the user
	}
	if (type == "again") {
		cout << "Would you like to do another calculation? (y,n) "; // Prompt user
	}

	// If I were to use cin >> returned, it would end the string at " ", and I don't want that.

	getline(cin, returned);
	return returned; // This function outputs the input of the user
}

void output(string doorCompany, int doorCostInterior, int doorCostExterior, int inDoorsPurchased, int exDoorsPurchased, double salesTax, double discountPercent, double financeCharge, string payMethod) {

	/*

	  _                 _
	 | |               (_)
	 | |     ___   __ _ _  ___
	 | |    / _ \ / _` | |/ __|
	 | |___| (_) | (_| | | (__
	 |______\___/ \__, |_|\___|
	               __/ |
		      |___/

	Here I wrote code to do all the math, assigning
	the outputs to variables.

	*/

	int DoorsPurchased = inDoorsPurchased + exDoorsPurchased;

	double inCost = doorCostInterior * inDoorsPurchased;
	double exCost = doorCostExterior * exDoorsPurchased;

	// Cash

	double cSubtotal = round((inCost + exCost) * (1 - discountPercent) * 100) / 100;


	double cTax = round((cSubtotal * salesTax) * 100) / 100;


	double cBill = round((cSubtotal + cTax) * 100) / 100;


	double cAverage = round((cBill / DoorsPurchased) * 100) / 100;

	// Finance

	double fSubtotal = round((inCost + exCost) * (1 + financeCharge) * 100) / 100;


	double fTax = round((fSubtotal * salesTax) * 100) / 100;


	double fBill = round((fSubtotal + fTax) * 100) / 100;


	double fAverage = round((fBill / DoorsPurchased) * 100) / 100;


	/*

	  _____  _           _                ____        _               _
	 |  __ \(_)         | |              / __ \      | |             | |
	 | |  | |_ ___ _ __ | | __ _ _   _  | |  | |_   _| |_ _ __  _   _| |_
	 | |  | | / __| '_ \| |/ _` | | | | | |  | | | | | __| '_ \| | | | __|
	 | |__| | \__ \ |_) | | (_| | |_| | | |__| | |_| | |_| |_) | |_| | |_
	 |_____/|_|___/ .__/|_|\__,_|\__, |  \____/ \__,_|\__| .__/ \__,_|\__|
		      | |             __/ |                  | |
		      |_|            |___/                   |_|

	This displays the output of the logic part, I rewrote this from scratch
	after seeing the output you wanted us to have.

	*/

	const string endm = ".00 \n"; // endl is short for end line, endm is short for end math, add .00 and new line
	const string SPACING = "    - ";

	cout << endl << "Invoice for " << doorCompany << endl << endl; // I could also use "\n"

	cout << "Cost for " << inDoorsPurchased << " interior doors is $" << inCost << endl;
	cout << "Cost for " << exDoorsPurchased << " exterior doors is $" << exCost << endl << endl;

	// If the payment method is cash, but then check if it has a decimal point, and if it doesn't use endm instead of endl.

	if (payMethod == "cash") {

		cout << SPACING << "If paying in cash for this purchase" << endl;

		if (remainder(cSubtotal, 2) == 0) {
			cout << SPACING << "The subtotal would be $" << cSubtotal << endm;
		}
		else {
			cout << SPACING << "The subtotal would be $" << cSubtotal << endl;
		}

		if (remainder(cTax, 0) == 0) {
			cout << SPACING << "The tax would be $" << cTax << endm;
		}
		else {
			cout << SPACING << "The tax would be $" << cTax << endl;
		}

		if (remainder(cBill, 2) == 0) {
			cout << SPACING << "The total bill would be $" << cBill << endm;
		}
		else {
			cout << SPACING << "The total bill would be $" << cBill << endl;
		}

		cout << SPACING << "The average cost per door would be " << cAverage << endl << endl;

	}

	// If the payment method is finance, but then check if it has a decimal point, and if it doesn't use endm instead of endl.

	if (payMethod == "finance") {
		cout << SPACING << "If financing this purchase" << endl;

		if (remainder(fSubtotal, 2) == 0) {
			cout << SPACING << "The subtotal would be $" << fSubtotal << endm;
		}
		else {
			cout << SPACING << "The subtotal would be $" << fSubtotal << endl;
		}

		if (remainder(fTax, 0) == 0) {
			cout << SPACING << "The tax would be $" << fTax << endm;
		}
		else {
			cout << SPACING << "The tax would be $" << fTax << endl;
		}

		if (remainder(fBill, 2) == 0) {
			cout << SPACING << "The total bill would be $" << fBill << endm;
		}
		else {
			cout << SPACING << "The total bill would be $" << fBill << endl;
		}

		cout << SPACING << "The average cost per door would be " << fAverage << endl << endl;

	}

	double saving = fAverage - cAverage;

	if (remainder(saving, 2) == 0) {
		cout << "By paying cash you would save $" << saving << endm << endl;
		return;
	}
	cout << "By paying cash you would save $" << saving << endl << endl;
}

void error() {
	cout << "Invalid input" << endl;
}

void input() {

	// Initilizing some variables and constants, these were originally hard coded constants but I made them changeable, they still default to these.

	int doorCostInterior = 500 /* The cost per each interior door */, doorCostExterior = 1200; // The cost per each exterior door
	double salesTax = .075 /* Sales tax */, discountPercent = .10 /* Discount percent */, financeCharge = .15; // Finance charge

/*

	  _____                   _
	 |_   _|                 | |
	   | |  _ __  _ __  _   _| |_
	   | | | '_ \| '_ \| | | | __|
	  _| |_| | | | |_) | |_| | |_
	 |_____|_| |_| .__/ \__,_|\__|
		     | |
		     |_|

	Here I ask for input and filter
	it to make sure it's valid, it
	asks for it repeatedly until it
	recieves a valid response.

*/

// First input

	string doorCompany = prompt("company"); // Prompt and set name of company selling the doors

	// Filter Method

	bool promptMethod = true;
	string paymentMethod = "ThisDoesn'tMatter";

	do {
		paymentMethod = prompt("method");

		std::transform(paymentMethod.begin(), paymentMethod.end(), paymentMethod.begin(), ::tolower); // https://notfaq.wordpress.com/2007/08/04/cc-convert-string-to-upperlower-case/

		if (paymentMethod == "cash" or paymentMethod == "finance") {
			promptMethod = false;
		}
		else {
			error();
		}
	} while (promptMethod == true);

	bool promptIn = true;

	int inDoorsPurchased; // Initialize variable

	do {

		// Error Handling Interior Doors

		try {
			string strNumInDoors = prompt("inDoors"); // Prompt and set number of interior doors as string
			inDoorsPurchased = stoi(strNumInDoors); // Set int val if valid input
			promptIn = false;
		}
		catch (invalid_argument) {
			error();
		}

	} while (promptIn == true);

	bool promptEx = true;

	int exDoorsPurchased;

	do {

		string strNumExDoors = prompt("exDoors"); // Prompt and set number of exterior doors as string

		// Error Handling Exterior Doors

		try {
			exDoorsPurchased = stoi(strNumExDoors); // Set as int value
			promptEx = false;
		}
		catch (invalid_argument) {
			error();
		}
	} while (promptEx == true);

	bool promptCustom = true;

	do {

		string custom = prompt("custom");

		if (custom == "y" or custom == "yes") {

			promptCustom = false;

			bool promptTax = true;

			do {
				try {
					string str = prompt("tax"); // Optimization
					if (stod(str) > 1 or stod(str) < 0) { error(); }
					salesTax = stod(str);
					promptTax = false;
				}
				catch (invalid_argument) {
					error();
				}
			} while (promptTax == true);

			bool promptDiscount = true;

			do {
				try {
					string str = prompt("discount"); // Optimization
					if (stod(str) > 1 or stod(str) < 0) { error(); }
					discountPercent = stod(str);
					promptDiscount = false;
				}
				catch (invalid_argument) {
					error();
				}
			} while (promptDiscount == true);

			bool promptCharge = true;

			do {
				try {
					string str = prompt("charge"); // Optimization
					if (stod(str) > 1 or stod(str) < 0) { error(); }
					financeCharge = stod(str);
					promptCharge = false;
				}
				catch (invalid_argument) {
					error();
				}
			} while (promptCharge == true);

			bool promptInPrice = true;

			do {
				try {
					doorCostInterior = stod(prompt("inPrice"));
					promptInPrice = false;
				}
				catch (invalid_argument) {
					error();
				}
			} while (promptInPrice == true);

			bool promptExPrice;

			do {
				try {
					doorCostExterior = stod(prompt("exPrice"));
					promptExPrice = false;
				}
				catch (invalid_argument) {
					error();
				}
			} while (promptExPrice == true);
		}
		else if (custom == "n" or custom == "no") { promptCustom = false; }
		else {
			error();
		}
	} 	while (promptCustom == true);


	// Send the data to the output
	output(doorCompany, doorCostInterior, doorCostExterior, inDoorsPurchased, exDoorsPurchased, salesTax, discountPercent, financeCharge, paymentMethod);

	bool final = true;

	do {
		// Ask if user would like to do another calculation
		string again = prompt("again");

		std::transform(again.begin(), again.end(), again.begin(), ::tolower); // https://notfaq.wordpress.com/2007/08/04/cc-convert-string-to-upperlower-case/

		if (again == "y" or again == "yes") {
			cout << endl;
			input();
			return;
		}
		else if (again == "n" or again == "no") {
			exit(0); // Exit, says online that system("anyArgument") is bad as it is system specific, slow, disliked by antivirus software etc.
		}
		error();
	} while (final == true);
}

int main() {
	input(); // Call function
	return 0;
}