001: #include <iostream>
002: #include <string>
003: 
004: using namespace std;
005: 
006: /**
007:    Turn a digit into its English name
008:    @param n an integer between 1 and 9
009:    @return the name of n ("one" . . . "nine")
010: */
011: string digit_name(int n)
012: {  
013:    if (n == 1) return "one";
014:    if (n == 2) return "two";
015:    if (n == 3) return "three";
016:    if (n == 4) return "four";
017:    if (n == 5) return "five";
018:    if (n == 6) return "six";
019:    if (n == 7) return "seven";
020:    if (n == 8) return "eight";
021:    if (n == 9) return "nine";
022:    return "";
023: }
024: 
025: /**
026:    Turn a number between 10 and 19 into its English name
027:    @param n an integer between 10 and 19
028:    @return the name of n ("ten" . . . "nineteen")
029: */
030: string teen_name(int n)
031: {  
032:    if (n == 10) return "ten";
033:    if (n == 11) return "eleven";
034:    if (n == 12) return "twelve";
035:    if (n == 13) return "thirteen";
036:    if (n == 14) return "fourteen";
037:    if (n == 15) return "fifteen";
038:    if (n == 16) return "sixteen";
039:    if (n == 17) return "seventeen";
040:    if (n == 18) return "eighteen";
041:    if (n == 19) return "nineteen";
042:    return "";
043: }
044: 
045: /**
046:    Give the English name of a multiple of 10
047:    @param n an integer between 2 and 9
048:    @return the name of 10 * n ("twenty" . . . "ninety")
049: */
050: string tens_name(int n)
051: {  
052:    if (n == 2) return "twenty";
053:    if (n == 3) return "thirty";
054:    if (n == 4) return "forty";
055:    if (n == 5) return "fifty";
056:    if (n == 6) return "sixty";
057:    if (n == 7) return "seventy";
058:    if (n == 8) return "eighty";
059:    if (n == 9) return "ninety";
060:    return "";
061: }
062: 
063: /**
064:    Turn a number into its English name
065:    @param n a positive integer < 1,000,000
066:    @return the name of n (e.g. "two hundred seventy four")
067: */
068: string int_name(int n)
069: {  int c = n; /* the part that still needs to be converted */
070:    string r; /* the return value */
071: 
072:    if (c >= 1000)
073:    {  
074:       r = int_name(c / 1000) + " thousand";
075:       c = c % 1000;
076:    }
077: 
078:    if (c >= 100)
079:    {  
080:       r = r + " " + digit_name(c / 100) + " hundred";
081:       c = c % 100;
082:    }
083: 
084:    if (c >= 20)
085:    {  
086:       r = r + " " + tens_name(c / 10);
087:       c = c % 10;
088:    }
089:    
090:    if (c >= 10)
091:    {  
092:       r = r + " " + teen_name(c);
093:       c = 0;
094:    }
095: 
096:    if (c > 0)
097:       r = r + " " + digit_name(c);
098: 
099:    return r;
100: }
101: 
102: int main()
103: {  
104:    int n;
105:    cout << "Please enter a positive integer: ";
106:    cin >> n;
107:    cout << int_name(n);
108:    return 0;
109: }
110: 
111: