Developer Documentation

int2roman.hh
1 #ifndef INT2ROMAN_HH
2 #define INT2ROMAN_HH
3
4 #include <string>
5
6 std::string int2roman( size_t decimal, size_t length = 30 )
7 {
8 assert( decimal > 0 && decimal < 1000 );
9
10 const size_t nrows = 4;
11 const size_t ncols = 4;
12
13 static size_t table_arabs[ nrows ][ ncols ] = { { 1000, 1000, 1000, 1000 },
14 { 900, 500, 400, 100 },
15 { 90, 50, 40, 10 },
16 { 9, 5, 4, 1 } };
17
18 static const char *table_romans[ nrows ][ ncols ] = { { "M", "M", "M", "M" },
19 { "CM", "D", "CD", "C" },
20 { "XC", "L", "XL", "X" },
21 { "IX", "V", "IV", "I" } };
22
23 size_t power; // power of ten
24 size_t index; // Indexes thru values to subtract
25
26 std::string roman = "";
27 roman.reserve(length);
28
29 for ( power = 0; power < nrows; power++ )
30 for ( index = 0; index < ncols; index++ )
31 while ( decimal >= table_arabs[ power ][ index ] )
32 {
33 roman += table_romans[ power ][ index ];
34 decimal -= table_arabs[ power ][ index ];
35 }
36
37 return roman;
38 }
39
40 #endif