//
// Program:  count-alpha
//
// Purpose:  print input in reverse order
//
// Input:  sequence of numbers x1, x2, .. xN, from standard input.
//
// Output:  x1, x2, .. xN printed to standard output in reverse order
//   (xN, .... x2, x1).  
//
//
// example of recursion:
//   function to count alphabetic characters in string, plus test program
//
// test program input:  character string S. 
// test program output:  number of alphabetic characters in S.

#include <iostream>
#include <cstdlib>		// has EXIT_SUCCESS
#include <iomanip>		// has setw()
#include <cctype>		// has isalpha()
using namespace std;

// Function to count alphabetic characters in string.
// Pre:  s contains a null-terminated string and n <= strlen(s)
// Post:  returns the number of alphabetic characters in s,
//        starting with s[n]
int countAlpha(const int n, const char s[])
{
  if (s[n] == '\0')
    return 0;
  else if (isalpha(s[n]))
    return 1 + countAlpha(n+1, s);
  else
    return countAlpha(n+1, s);
}

// Main program.
int main(void)
{
  const int BUFFSIZE = 1000;
  char instring[BUFFSIZE];

  cout << "Enter a character string:\n";
  // setw() guards against overrunning end of "instring" array.
  cin >> setw(BUFFSIZE) >> instring;

  cout << '"' << instring << '"' << " contains " 
       << countAlpha(0, instring) << " alphabetic characters\n";

  return EXIT_SUCCESS;
}