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60 lines
1.7 KiB
Nim
60 lines
1.7 KiB
Nim
#
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#
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# Nim's Runtime Library
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# (c) Copyright 2011 Philippe Lhoste
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#
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# See the file "copying.txt", included in this
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# distribution, for details about the copyright.
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#
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## Module for converting an integer to a Roman numeral.
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## See http://en.wikipedia.org/wiki/Roman_numerals for reference.
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##
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## **Warning:** This module will be moved out of the stdlib and into a
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## Nimble package, don't use it.
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const
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RomanNumeralDigits* = {'I', 'i', 'V', 'v', 'X', 'x', 'L', 'l', 'C', 'c',
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'D', 'd', 'M', 'm'} ## set of all characters a Roman numeral may consist of
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proc romanToDecimal*(romanVal: string): int =
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## Converts a Roman numeral to its int representation.
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result = 0
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var prevVal = 0
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for i in countdown(romanVal.len - 1, 0):
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var val = 0
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case romanVal[i]
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of 'I', 'i': val = 1
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of 'V', 'v': val = 5
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of 'X', 'x': val = 10
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of 'L', 'l': val = 50
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of 'C', 'c': val = 100
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of 'D', 'd': val = 500
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of 'M', 'm': val = 1000
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else:
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raise newException(EInvalidValue, "invalid roman numeral: " & $romanVal)
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if val >= prevVal:
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inc(result, val)
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else:
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dec(result, val)
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prevVal = val
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proc decimalToRoman*(number: range[1..3_999]): string =
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## Converts a number to a Roman numeral.
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const romanComposites = [
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("M", 1000), ("CM", 900),
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("D", 500), ("CD", 400), ("C", 100),
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("XC", 90), ("L", 50), ("XL", 40), ("X", 10), ("IX", 9),
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("V", 5), ("IV", 4), ("I", 1)]
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result = ""
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var decVal: int = number
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for key, val in items(romanComposites):
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while decVal >= val:
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dec(decVal, val)
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result.add(key)
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when isMainModule:
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for i in 1 .. 3_999:
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assert i == i.decimalToRoman.romanToDecimal
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