Stuck on commas when entering numbers

[wpenguin]

Hello,
So, I am fairly new to programming and I've been trying to implement some other previously posted solutions to a problem, but so far I can't figure out how to adapt what I've found to my program. The program I have is from a tutorial where the user enters two points on a line, and then the program calculates the mid-point and slope.

I want to modify it from it's initial form so that co-ordinates can be input in (x,y) fashion. Right now the user has to enter the x-coordinate, enter a space, and then enter the y-coordinate (lame...)

I saw people using SStream and using that to either write functions to ignore the comma or similar things for converting one file into an array, but not quite what I am trying here. Any hints anyone could send me? Thanks!!

// program to determine slope of a line

#include <ios>
#include <iostream>
#include <istream>
#include <limits>

using namespace std;

void myflush ( istream& in )
{ 
	in.ignore ( numeric_limits<streamsize>::max(), '\n' );
	in.clear();
}

void mypause()  // have to press ENTER twice for some reason...
{ 
  cout << endl << "Press [Enter] to exit . . .";
  cin.get();
} 

int main()
{

		float x1, x2, y1, y2, mdpt1, mdpt2, slope; // must use float, double, or 
			long double (integer will not work)

		cout << "This program will help you calculate the mid-point and 
			slope of a line." << endl << endl;
		cout << "Please input the co-ordinates of the first point " << endl 
			<< "(x and y with a space in between): " << endl << endl;
		
		cin >> x1 >> y1;
		cout << "Thank you, please input the value of the second point: " << endl;
		
		cin >> x2 >> y2;

		mdpt1 = (x1 + x2) / 2;  //begin calculation
		mdpt2 = (y1 + y2) / 2;

		slope = (y2 - y1) / (x2 - x1);

		cout << "The midpoint of the line is (" << mdpt1 << ", " << mdpt2 
			<< ")." <<endl << endl; //send to screen
		cout << "The slope of the line is " << slope << "." << endl << endl;
		cout << "Thanks for using this program." << endl;

		myflush ( cin );
		mypause();

		cin.get();   // still have to press enter twice...
	
}

[Cubbi]

Do you expect exactly the (x,y) format (parenthesis, number, comma, number, parenthesis) or just x,y (number, comma, numer)?

Either way, you could read the non-digits as char:

char c1,c2,c3;
double x1,y1;
cin >> c1 >> x1 >> c2 >> y1 >> c3; // or cin >> x1 >> c1 >> y1;
if(! cin || c1 != '(' || c2 != ',' || c3 != ')')
{
    // handle the input error
}

,

You could also modify the inputs stream to treat commas as space (takes a few lines of boilerplate code), or you could use a more serious parser like regex or boost.spirit.

Also, if you're looking for exactly (x,y) format, you could simply read the user input into a complex number. The complex numbers in C++ use exactly that syntax: parenthesis, number, comma, number, parenthesis.

[wpenguin]

Thank you for your help! I re-worked it as follows for the first set of inputs.
This ignores the parenthesis part because I want the user to enter the coordinates as just integers with a comma in between.

int main()
{
		char c1,c2;
		double x1, x2, y1, y2, mdpt1, mdpt2, slope;
		cout << "This program will help you calculate the mid-point and 
			slope of a line." << endl << endl;
		cout << "Please input the co-ordinates of the first point " << endl << 
			"using the format x,y " << endl << endl;

		
		cin >> x1 >> c1 >> y1;
		if(! cin || c1 != (','))
		{

		}

I intend for the input to be without the parenthesis. However, what I am beginning to notice is that if I input something like a symbol, an extra space, or something other than the request sequence of an integer, a comma, and a second integer, the program just goes to the next line.

You could also modify the inputs stream to treat commas as space (takes a few lines of boilerplate code),
or you could use a more serious parser like regex or boost.spirit

Should I pursue these ways of handling all incorrect inputs by the user or are these specific to just dealing with certain characters like the comma?