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72 lines
1.9 KiB
Nim
72 lines
1.9 KiB
Nim
discard """
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file: "tromans.nim"
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output: "success"
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"""
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import
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strutils
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## Convert an integer to a Roman numeral
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# See http://en.wikipedia.org/wiki/Roman_numerals for reference
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proc raiseInvalidValue(msg: string) {.noreturn.} =
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# Yes, we really need a shorthand for this code...
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var e: ref EInvalidValue
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new(e)
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e.msg = msg
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raise e
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# I should use a class, perhaps.
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# --> No. Why introduce additional state into such a simple and nice
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# interface? State is evil. :D
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proc RomanToDecimal(romanVal: string): int =
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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: raiseInvalidValue("Incorrect character in roman numeral! (" &
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$romanVal[i] & ")")
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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(decValParam: int): string =
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# Apparently numbers cannot be above 4000
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# Well, they can be (using overbar or parenthesis notation)
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# but I see little interest (beside coding challenge) in coding them as
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# we rarely use huge 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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if decValParam < 1 or decValParam > 3999:
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raiseInvalidValue("number not representable")
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result = ""
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var decVal = decValParam
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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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for i in 1..100:
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if RomanToDecimal(DecimalToRoman(i)) != i: quit "BUG"
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for i in items([1238, 1777, 3830, 2401, 379, 33, 940, 3973]):
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if RomanToDecimal(DecimalToRoman(i)) != i: quit "BUG"
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echo "success" #OUT success
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