Question

How can i read in a specific format using cin?
Example:-for reading a complex number, I would like the user to enter it as usual:x+yi,
so i want something like this:
cin>>x>>”+”>>y>>”i”;
But this is giving an error.What is the right way?Help greatly appreciated.

Answer 1

A very simple solution:

char plus,img;
double x,y;
cin>> x >> plus >> y >> img;
if (plus!='+' || img!='i')     ...error

In “real life” code you build/use a class complex, and overload the operator >>.

I try it in Ideone: http://ideone.com/ZhSprF

#include <iostream>
using namespace std;

int main() 
{
    char plus{},img{};
    double x{},y{};
    cin>> x >> plus >> y >> img;
    if (plus!='+' || img!='i') 
        cout << "\nError: "<< "x=" << x <<", plus="  << plus <<", y="  << y <<", img="  << img;
    else
        cout << "\nComplex: " << x << plus << y << img;


    return 0;
}

stdin: 3 + 4i –> stdout: Complex: 3+4i

stdin: 1E4L1e3g –> stdout: Error: x=10000, plus=L, y=1000, img=g

stdin: a+3i –> stdout: Error: x=0, plus=, y=0, img=

stdin: 1e3+93E-2i –> stdout: Complex: 1000+0.93i