romannume.def

DEFINITION MODULE RomanNumerals;

(* convert to/from strings of Roman Numerals to cardinal values *)
(* J. Andrea, Sept.5/91 *)
(* This code may be freely used and distributed, it may not be sold. *)


EXPORT QUALIFIED FromRoman, ToRoman;


PROCEDURE FromRoman( numerals :ARRAY OF CHAR; VAR value :CARDINAL );
(*
 Convert from a Roman numeral string to a number.
 Zero is returned if the given string is an invalid roman numeral,
 remember that Romans didn't know the concept of zero.

 This routine is fairly robust, it will attempt to convert
 improper roman numbers, but the result may be strange.

 It is also very forgiving of badly formed roman numerals
 and will always produce a result, though it may not be what is expected
 but remember, garbage in -> garbage out.

 Things like this will get translated:

 iv = 4          this is normal, and properly formed
 vv = 10         not proper, but acceptable
 iiv = 3         this is improperly formed, but result is as expected
 iiiiv = 1       same as above
 iiiiiv = 10     the group of 5 i's is not smaller than V so add rather
                 than subtract
 vvx = 20        again, VV is not smaller than X, so add them
 ivx = 6         think of it as ((iv)x) = 10 - (5-1) = 10-4 = 6
 viiiiii = 1     5,6 the 5 is smaller so its subtracted from 6
 ivvx = 1        i(vv)x = 1(10)10 = (9)10 = 1
*)


PROCEDURE ToRoman( value :CARDINAL; VAR numerals :ARRAY OF CHAR );
(*
 Convert from a cardinal value to a Roman numeral string.
 An impossible number returns an empty string or if the output string is
 not long enough to hold the value then an empty string is also returned.
*)


END RomanNumerals.