Calculator for Stroustrup's Book - Chapter 3 Exercise

[DragonOsman]

I wrote this calculator code and it's working fine, but I wanted to ask if I'm doing the error-handling fine or not. As it is now, the program will exit immediately after the exception handling code is done, but I'm wondering if that's fine for this program. [Note: as of Chapter 3, exceptions still haven't been introduced yet, but I already know about them so I decided to use them.]

Here's the code:

// chap3_ex10.cpp : Defines the entry point for the console application.
// Osman Zakir
// 5 / 24 / 2016
// Programming: Principles and Practice using C++ 2nd Edition Chapter 3 Exercise 10
// This is a very simple calculator. Only accepts one operation and two numbers

#include "std_lib_facilities.h"

double get_number();
string get_operaton();
double calculate_result(const double x, const double y, const string& operation);
void print_result(const double result);

int main()
{
	try
	{
		cout << "Enter a number: ";
		double x = get_number();
		cout << "Enter another number: ";
		double y = get_number();
		cout << "Enter an operation: ";
		string operation = get_operaton();
		double result = calculate_result(x, y, operation);
		print_result(result);
		keep_window_open();
	}
	catch (const runtime_error& r)
	{
		cerr << r.what() << "\n";
		keep_window_open();
		return 1;
	}
	catch (const exception& e)
	{
		cerr << e.what() << "\n";
		keep_window_open();
		return 2;
	}
	catch (...)
	{
		cerr << "Error: Unexpected exception caught\n";
		keep_window_open();
		return 3;
	}
}

double get_number()
{
	double number = 0;
	cin >> number;
	cin.ignore(32767, '\n');
	return number;
}

string get_operaton()
{
	string operation;
	cin >> operation;
	cin.ignore(32767, '\n');
	return operation;
}

double calculate_result(const double x, const double y, const string& operation)
{
	if (operation == "+")
	{
		return x + y;
	}
	else if (operation == "-")
	{
		return x - y;
	}
	else if (operation == "*")
	{
		return x * y;
	}
	else if (operation == "/")
	{
		return x / y;
	}
	else if (operation != "/" || operation != "*" || operation != "+" || operation != "-")
	{
		error("Invalid operation!");
	}
}

void print_result(const double result)
{
	cout << "Your answer is: " << result << "\n";
}

The library access header for the book, std_lib_facilities.h, has iostream and stdexcept, as well as the file that defines std::numeric_limits, among other important header files. I could bring it here for anyone who needs it, but this post is already going to get too long so I'll have to do that in another post.