Lee's Roman Numeral
Converter
by Lee
K. Seitz
Code Explanation
I began getting requests from students
for the source code to my Arabic to Roman numeral converter not
too long after I put it on the Internet. I'm a firm believer
in students doing their own work, so I will not give the source
to anyone. (Besides, it's written in Perl, which allows me to
do some things not easily done in C.) It has nothing to do with
planning on making money from such a simple algorithm. Although
I won't give out the source, here's a brief and purposely
vague explanation of how it works:
I start with an array of the Roman numeral
"digits". (Perl is great for manipulating text by breaking
each character of a string into an array and such.) Then I determine
the length of the input (decimal) number. This tells me where
in the array to set my pointers for ones, fives, and tens. After
this is set up, I just iterate through each digit with a big
if-else statement (Perl doesn't have a case statement.) for each
digit 1-9 (zeroes are meaningless in Roman numerals), building
my string.
Here's an exmple of the steps for "14":
length(Input) = 2, so One="X",
Five="L", Ten="C"
if (1 == Input) . . . yep!
String = String + One
Remaining digits in Input, so now One="I",
Five="V", Ten="X"
if (1 == Input) . . . nope!
else if (2 == Input) . . . nope!
else if (3 == Input) . . . nope!
else if (4 == Input) . . . yep!
String = String + One + Five
No more digits in Input, return String
("XIV")
Since I wrote the converter, I've come
up with a slightly better way of doing it involving two arrays
of Roman numeral "digits" instead of one. This is left
as an exercise for the reader. Also, a friend of mine independently
came up with something better than nine else/if statements. This,
also, is left as an excercise for the reader.
