// sample code to count vowels in input
//
// Compile:
//      g++ -std=c++14 -Wall countvowels.cpp
// Usage:
//      a.exe file
// or
//      a.exe < file

#include <iostream>
#include <fstream>
#include <cctype>               // for tolower

using namespace std;

// uses command-line arguments to set input; will read from standard input
//     if no command-line argument is specified
// Precondition: called once
void set_input(int argc, char *argv[]) {
   static bool called = false;
   if ( called ) {
      cerr << "set_input cannot be called twice." << endl;
      exit(1);
   }
   called = true;
   static ifstream alternative_input; // used if have filename on command line
   if (argc > 0 && argv[1] != nullptr && argv[1][0] != 0) {
      alternative_input.open(argv[1]);
      if (!alternative_input) {
         cerr << "Could not open " << argv[1] << " for input." << endl;
         exit(1);
      }
      // this magic sets the read buffer for cin to the read buffer for
      //   the input stream (redirecting input from the named file)
      cin.rdbuf(alternative_input.rdbuf());
      cerr << "Reading from " << argv[1] << endl;
   }
}

int main(int argc, char *argv[]) {
   set_input(argc, argv);
   
   // read characters from input, counting vowels
   int vowels = 0;
   char ch;
   cin >> ch;
   while ( cin ) {
      ch = tolower(ch);
      if ( ch == 'a' || ch == 'e' || ch == 'i' || ch == 'o' || ch == 'u' )
         vowels++;
      cin >> ch;
   }

   cout << "Number of vowels in input: " << vowels << endl;
   
   return 0;
}