C++ Bisection Method

Implementation of Bisection Method written in C++.

// ? 2017 TheFlyingKeyboard and released under MIT License
// theflyingkeyboard.net

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

using namespace std;

static double function(double x);

int main() {
  double intervalBegin;
  double intervalEnd;
  double middle;
  double precision;

  cout << "Enter begining of interval: ";
  cin >> intervalBegin;

  cout << "Enter end of interval: ";
  cin >> intervalEnd;

  cout << "Enter precision of method: ";
  cin >> precision;

  if (function(intervalBegin) * function(intervalEnd) > 0.0f)
  {
    cout << "Function has same signs at ends of interval";
    return -1;
  }

  while (abs(intervalBegin - intervalEnd) > precision)
  {
    middle = (intervalBegin + intervalEnd) / 2.0f;

    cout << "X: " << middle << endl;

    if (function(intervalBegin) * function(middle) < 0.0f)
    {
      intervalEnd = middle;
    }
    else
    {
      intervalBegin = middle;
    }
  }

  int a;
  cin >> a; //Wait before exiting

  return 0;
}

static double function(double x)
{ //x^2 + 2x -1
  return x * (x + 2) - 1;
}