Is This Simple Calculator Coded Correctly? C++

f ben isaac (76)
1. Simple calculator - nothing fancy

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/**program description:
 *
 * simple calculator written for beginners. 
 * This program asks user to enter an arithmetic
 * expression that contains two numbers and one 
 * operator. User will be given the result of the 
 * calculation. Operators allowed to be used 
 * are: + - * / % ...
 *
 * Author: X-Shab
 * Copyright 2008 - 2009
 *
 */

#include<iostream>
#include<string>
using namespace std;

const string EXIT = "-1";

void add(float num1, float num2)
{
	cout<<"Result is: "<< num1 + num2 <<endl;
}

void subtract(float num1, float num2)
{
	cout<<"Result is: "<< num1 - num2 <<endl;
}

void multiply(float num1, float num2)
{
	cout<<"Result is: "<< num1 * num2 <<endl;
}

void divide(float numerator, float denominator)
{
	if (denominator != 0)
		cout<<"Result is: "<< numerator / denominator <<endl;
	else
		cout<<"You can not divide by denominator\n";
}

void modulus(float num1, float num2)
{
	cout<<"Result is: "<<  (int)num1 % (int)num2 <<endl;
}

int main(void)
{
	string mathematicalOperation;
	float num1, num2;
	char operatorSign;
	
	cout << "Please enter an arithmetic expression (-1 to Exit)\n";
	cin >> mathematicalOperation;

	//search for operator sign and perform calculation
	while(mathematicalOperation.compare(EXIT))
	{
		int getFirstDigitIndex = mathematicalOperation.find_first_of("0123456789");
		int operatorSignIndex = mathematicalOperation.find_first_of("+-*/%", getFirstDigitIndex);
		
		if (operatorSignIndex != -1)
		{	
			operatorSign = mathematicalOperation.at(operatorSignIndex);
		
			string firstNumber = mathematicalOperation.substr(0,operatorSignIndex);
			string secondNumber = mathematicalOperation.substr(operatorSignIndex + 1);

			//convert numbers from string to float
			num1 = (float)atof(firstNumber.c_str());
			num2 = (float)atof(secondNumber.c_str());

			switch(operatorSign)
			{
				case '+':
					add(num1,num2);
					break;
				case '-':
					subtract(num1,num2);
					break;
				case '*':
					multiply(num1,num2);
					break;
				case '/':
					divide(num1,num2);
					break;
				case '%':
					modulus(num1,num2);
					break;
			}
		}
		
		cout<<"Please Enter Another Expression or Enter -1 to Exit:\n";
		cin>>mathematicalOperation;
	}

	cout<<"SEE YOU LATER!\n";

	return 0;
}




2. Simple calculator using function template

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/**program description:
 *
 * simple calculator written for intermediates. 
 * This program asks user to enter an arithmetic
 * expression that contains two numbers and one 
 * operator. User will be given the result of the 
 * calculation. Operators allowed to be used 
 * are: + - * / % ... 
 *
 * Author: X-Shab
 * Copyright 2008 - 2009
 *
 */

#include<iostream>
#include<string>
using namespace std;

const string EXIT = "-1";

template <class T>
void performCalculation(T num1, T num2, const char operatorSign)
{
	switch(operatorSign)
	{
		case '+':
			cout<<"Result is: "<< num1 + num2 <<endl;
			break;
		case '-':
			cout<<"Result is: "<< num1 - num2 <<endl;
			break;
		case '*':
			cout<<"Result is: "<< num1 * num2 <<endl;
			break;
		case '/':
			if (num2 != 0)
				cout<<"Result is: "<< num1 / num2 <<endl;
			else
				cout<<"You Can Not Divide by Zero\n";
			break;
		case '%':
			cout<<"Result is: "<<  (int)num1 % (int)num2 <<endl;
			break;
		default:
			cout<<"wrong operator sign"<<endl;
	}
}

int main(void)
{
	string mathematicalOperation;
	float num1, num2;
	char operatorSign;
	
	cout << "Please enter an arithmetic expression (-1 to Exit)\n";
	cin >> mathematicalOperation;

	while(mathematicalOperation.compare(EXIT))
	{
		int getFirstDigitIndex = mathematicalOperation.find_first_of("0123456789");
		int operatorSignIndex = mathematicalOperation.find_first_of("+-*/%", getFirstDigitIndex);
		
		if (operatorSignIndex != -1)
		{	
			operatorSign = mathematicalOperation.at(operatorSignIndex);
		
			string firstNumber = mathematicalOperation.substr(0,operatorSignIndex);
			string secondNumber = mathematicalOperation.substr(operatorSignIndex + 1);

			//convert numbers from string to float
			num1 = (float)atof(firstNumber.c_str());
			num2 = (float)atof(secondNumber.c_str());

			performCalculation(num1, num2, operatorSign);

		}
		
		cout<<"Please Enter Another Expression or Enter -1 to Exit:\n";
		cin>>mathematicalOperation;
	}

	cout<<"SEE YOU LATER!\n";

	return 0;
}


1. Is the template in the second example is structured and used correctly?
2. I tried to make my code easy to understand by putting descriptive names. Do you find it easy to follow? Is the code structure well written?
eker676 (427)
I don't have experience with templates but if it compiles then your good. It looks alright to me.

The your code is easy to follow in my opinion. Some of the names are a hair long but I have no question about what is supposed to happen.

By code structure do you mean tabs/spacing etc.?
That code is perfectly spaced and tabbed. It's nice on the eyes.
f ben isaac (76)
Thanks. Glad to hear this ;-) ....
f ben isaac (76)
I found that template function should be called as

performCalculation<float>(num1, num2, operatorSign); even though
performCalculation(num1, num2, operatorSign); worked fine

Regards
Bazzy (6281)
performCalculation(num1, num2, operatorSign);
works as the template argument is deduced from the passed function argument type
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