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#
#
# Nimrod's Runtime Library
# (c) Copyright 2011 Philippe Lhoste
#
# See the file "copying.txt", included in this
# distribution, for details about the copyright.
#
## Module for converting an integer to a Roman numeral.
## See http://en.wikipedia.org/wiki/Roman_numerals for reference.
const
RomanNumeralDigits* = {'I', 'i', 'V', 'v', 'X', 'x', 'L', 'l', 'C', 'c',
'D', 'd', 'M', 'm'} ## set of all characters a Roman numeral may consist of
proc romanToDecimal*(romanVal: string): int =
## Converts a Roman numeral to its int representation.
result = 0
var prevVal = 0
for i in countdown(romanVal.len - 1, 0):
var val = 0
case romanVal[i]
of 'I', 'i': val = 1
of 'V', 'v': val = 5
of 'X', 'x': val = 10
of 'L', 'l': val = 50
of 'C', 'c': val = 100
of 'D', 'd': val = 500
of 'M', 'm': val = 1000
else:
raise newException(EInvalidValue, "invalid roman numeral: " & $romanVal)
if val >= prevVal:
inc(result, val)
else:
dec(result, val)
prevVal = val
proc decimalToRoman*(number: range[1..3_999]): string =
## Converts a number to a Roman numeral.
const romanComposites = [
("M", 1000), ("CM", 900),
("D", 500), ("CD", 400), ("C", 100),
("XC", 90), ("L", 50), ("XL", 40), ("X", 10), ("IX", 9),
("V", 5), ("IV", 4), ("I", 1)]
result = ""
var decVal = number
for key, val in items(romanComposites):
while decVal >= val:
dec(decVal, val)
result.add(key)
when isMainModule:
import math
randomize()
for i in 1 .. 100:
var rnd = 1 + random(3990)
assert rnd == rnd.decimalToRoman.romanToDecimal
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