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//===--- RomanNumbers.swift -----------------------------------------------===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 2018 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See https://swift.org/LICENSE.txt for license information
// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
//
//===----------------------------------------------------------------------===//
import TestsUtils
// Mini benchmark implementing roman numeral conversions to/from integers.
// Measures performance of Substring.starts(with:), dropFirst and String.append
// with very short string arguments.
let t: [BenchmarkCategory] = [.api, .String, .algorithm]
let n = 270
public let benchmarks = [
BenchmarkInfo(
name: "RomanNumbers2",
runFunction: {
checkId($0, upTo: n, { $0.romanNumeral }, Int.init(romanSSsWdF:)) },
tags: t),
]
@inline(__always)
func checkId(_ n: Int, upTo limit: Int, _ itor: (Int) -> String,
_ rtoi: (String) -> Int?) {
for _ in 1...n {
check(
zip(1...limit, (1...limit).map(itor).map(rtoi)).allSatisfy { $0 == $1 })
}
}
let romanTable: KeyValuePairs<String, Int> = [
"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,
]
extension BinaryInteger {
// Imperative Style
// See https://www.rosettacode.org/wiki/Roman_numerals/Encode#Swift
// See https://www.rosettacode.org/wiki/Roman_numerals/Decode#Swift
var romanNumeral: String {
var result = ""
var n = self
for (numeral, value) in romanTable {
while n >= value {
result += numeral
n -= Self(value)
}
}
return result
}
init?(romanSSsWdF number: String) {
self = 0
var raw = Substring(number)
for (numeral, value) in romanTable {
while raw.starts(with: numeral) {
self += Self(value)
raw = raw.dropFirst(numeral.count)
}
}
guard raw.isEmpty else { return nil }
}
}
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