#include "library.h"

const string smalls[] =
  { "zero", "one", "two", "three", "four", "five", "six", "seven",
    "eight", "nine", "ten", "eleven", "twelve", "thirteen", "fourteen", 
    "fifteen", "sixteen", "seventeen", "eighteen", "nineteen" };

const string tens[] =
  { "zero", "ten", "twenty", "thirty", "forty", "fifty", "sixty",
    "seventy", "eighty", "ninety" };

void say(const int n)
    // guaranteed OK for all inputs
    // guaranteed perfect for all n 0 to 19
    // will remain perfect for that range so long
    // as I don't change anything before this (*) point.

{ if (n < 0)
    print("I don't know how to say that");
  else if (n < 20)
    print( smalls[n] );
                       // * "this" point
  else
    print( "I don't know how to say that" ); }

bool again()
{ while (true)
  { print("go again (y or n)? ");
    const string answer = read_string();
    if (answer == "y")
      return true;
    if (answer == "n")
      return false; } }

void main()
{ while ( again() )
  { print("number? ");
    const int x = read_int();
    say(x);
    new_line(); } }