// Code derived from Stroustrup's PPP2 book
// § 4.4.1.1 if-statements
//  -and beginning on p 103

#include <iostream>

using std::cin;
using std::cout;

// convert from inches to centimeters or centimeters to inches
// a whitespace-separated suffix ‘i’ or ‘c’ indicates the unit of the input
// any other suffix is an error
int main()
{
  constexpr double cm_per_inch = 2.54;  // number of centimeters in an inch
  double           length      = 1;     // length in inches or centimeters
  char             unit        = ' ';   // a space is not a unit

  cout << "Please enter a length followed by a separate unit (c or i):\n";
  cin >> length >> unit;

  if (unit == 'i')
    cout << length << "in == " << cm_per_inch * length << "cm\n";
  else if (unit == 'c')
    cout << length << "cm == " << length / cm_per_inch << "in\n";
  else
    cout << "Sorry, I don't know a unit called '" << unit << "'\n";
}