digits2.cpp

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#include <iostream>
using namespace std;
#include "prompt.h"

// prelude to recursion: print English form of each digit
// in an integer: 123 -> "one two three"

void PrintDigit(int num)
// precondition: 0 <= num < 10
// postcondition: prints english equivalent, e.g., 1->one,...9->nine     
{
    if (0 == num)       cout << "zero";
    else if (1 == num)  cout << "one";
    else if (2 == num)  cout << "two";
    else if (3 == num)  cout << "three";
    else if (4 == num)  cout << "four";
    else if (5 == num)  cout << "five";
    else if (6 == num)  cout << "six";
    else if (7 == num)  cout << "seven";
    else if (8 == num)  cout << "eight";
    else if (9 == num)  cout << "nine";
    else cout << "?";
}

void PrintOne(long number)
// precondition: 0 <= number < 10
// postcondition: prints English equivalent of number
{
    if (0 <= number && number < 10)
    {   PrintDigit(number);
    }
}

void PrintTwo(long int number)
// precondition: 10 <= number < 100
// postcondition: prints English equivalent of number
{
    if (10 <= number && number < 100)
    {   PrintOne(number / 10);
        cout << " ";
        PrintDigit(number % 10);
    }
}

void PrintThree(long int number)
// precondition: 100 <= number < 1000
// postcondition: prints English equivalent of number
{
    if (100 <= number && number < 1000)
    {   PrintTwo(number / 10);
        cout << " ";
        PrintDigit(number % 10);
    }
}

void PrintFour(long int number)
// precondition: 1000 <= number < 10,000
// postcondition: prints English equivalent of number
{
    if (1000 <= number && number < 10000)
    {   PrintThree(number / 10);
        cout << " ";
        PrintDigit(number % 10);
    }
}

int main()
{
    int number = PromptRange("enter an integer",1000,9999);
    PrintFour(number);
    cout << endl;
    
    return 0;
}