#include "library.h"

   // PROTOTYPES, allow functions to be used before their definitions
void print_0_to_19(const int d);
     // absolutely tested and perfect, speaks any number 0 .. 19

void print_multiple_of_10(const int d);
     // perfect, says any number 10, 20, 30, ..., up to 90

void print_20_to_99(const int n);
     // perfect for any number 20, 21, 22, ..., 99

void print_100_to_999(const int n);
     // perfect for any number 100 ... 999


void say_number(const int n)
     // guaranteed perfect for any number 0 ... 999
{ 
  if (n < 20)
    print_0_to_19(n);
    
  else if (n < 100)
    print_20_to_99(n);
    
  else if (n < 1000)
    print_100_to_999(n);

  else if (n < 1000000)
  { say_number(n / 1000);
    print(" thousand");
    const int last3 = n % 1000;
    if (n % 1000 > 0)
    { print(" ");
      if (last3 < 100)
        print("and ");
      say_number(n % 1000); } }

  else
  { print("Sorry, I don't know how to say ");
    print(n);
    print(" yet.\n"); } }



void print_100_to_999(const int n)
{ const int hundreds = n / 100,
            remainder = n % 100;
  say_number(hundreds);
  print(" hundred");
  if (remainder != 0)
  { print(" and ");
    say_number(remainder); } }	    

void print_20_to_99(const int n)
                         // example:   if     n    is 47
                         //          then  n/10*10 is 40
                         //           and   n%10   is  7
{ print_multiple_of_10(n/10*10);
  if (n % 10 != 0)
  { print(" ");
    print_0_to_19(n%10); } }

void test(const int n)
{ print("testing ");
  print(n);
  print(": '");
  say_number(n);
  print("'\n"); }


void main()
{ test(27);
  test(138);
  test(509);
  test(999);
  test(12);
  test(4);
  test(40);
  while (true)
  { print("enter a test number (negative to stop): ");
    const int t = read_int();
    if (t < 0) break;
    test(t); }
  print("Test over\n"); }

void print_0_to_19(const int d)
{ if (d == 0)
    print("zero");
  else if (d == 1)
    print("one");
  else if (d == 2)
    print("two");
  else if (d == 3)
    print("three");
  else if (d == 4)
    print("four");
  else if (d == 5)
    print("five");
  else if (d == 6)
    print("six");
  else if (d == 7)
    print("seven");
  else if (d == 8)
    print("eight");
  else if (d == 9)
    print("nine");
  else if (d == 10)
    print("ten");
  else if (d == 11)
    print("eleven");
  else if (d == 12)
    print("twelve");
  else if (d == 13)
    print("thirteen");
  else if (d == 14)
    print("fourteen");
  else if (d == 15)
    print("fifteen");
  else if (d == 16)
    print("sixteen");
  else if (d == 17)
    print("seventeen");
  else if (d == 18)
    print("eighteen");
  else if (d == 19)
    print("nineteen");
  else 
    print("\n**** ERROR ****\n"); }

void print_multiple_of_10(const int d)
{ if (d == 10)
    print("ten");
  else if (d == 20)
    print("twenty");
  else if (d == 30)
    print("thirty");
  else if (d == 40)
    print("forty");
  else if (d == 50)
    print("fifty");
  else if (d == 60)
    print("sixty");
  else if (d == 70)
    print("seventy");
  else if (d == 80)
    print("eighty");
  else if (d == 90)
    print("ninety");
  else 
    print("\n**** ERROR ****\n"); }