Parsing fractions from text

fractionParser.swift

import UIKit

let fractionRegExPattern = #"(?<neg>-?){0,1}(?:\s){0,1}(?:(?<whole>\d+)\s)?(?<numerator>\d+)\/(?<denominator>\d+)"#

func parseResult(_ match:NSTextCheckingResult, canidateString:String) -> (Int?, Int, Int) {
    var mulitplier = 1
    var wholeNumber: Int?
    
    var numerator: Int?
    var denominator: Int?
    
    if canidateString[(Range(match.range(withName: "neg"), in: canidateString)!)] == "-" {
        mulitplier = -1
        print("negative!")
    }
    
    if let wholeNumberRange = Range(match.range(withName: "whole"), in: canidateString) {
        wholeNumber = Int(canidateString[wholeNumberRange])
        if wholeNumber != nil {
            wholeNumber = wholeNumber! * mulitplier
        }
    }
    
    if let numeratorRange = Range(match.range(withName: "numerator"), in: canidateString) {
        numerator = Int(canidateString[numeratorRange])
        if wholeNumber == nil {
            numerator = numerator! * mulitplier
        }
    }
    
    if let denominatorRange = Range(match.range(withName: "denominator"), in: canidateString) {
        denominator = Int(canidateString[denominatorRange])
    }
    
    
    if numerator == nil || denominator == nil {
        fatalError("how did they not get found???!!!")
    }
    
    return (whole:wholeNumber, numerator:numerator!, denominator:denominator!)
}

func findAll(in canidateString:String) -> [(whole:Int?, numerator:Int, denominator:Int)] {
    let regex = try? NSRegularExpression(pattern: fractionRegExPattern, options: .caseInsensitive)
  
  var foundFractions:[(whole:Int?, numerator:Int, denominator:Int)] = []

    if let matches = regex?.matches(in: canidateString, options: [], range: NSRange(location: 0, length: canidateString.utf16.count)) {
        
        for m in 0..<matches.count {
            foundFractions.append(parseResult(matches[m], canidateString: canidateString))
        }
    }
    return foundFractions
}

func findFirst(in canidateString:String) -> (whole:Int?, numerator:Int, denominator:Int)? {
    guard let regex = try? NSRegularExpression(pattern: fractionRegExPattern, options: .caseInsensitive) else {
        print("bad regex")
        return nil
    }
    if let match = regex.firstMatch(in: canidateString, options: [], range: NSRange(location: 0, length: canidateString.utf16.count)) {
        return parseResult(match, canidateString: canidateString)
    }
    return nil
}








let testStrings = [
    "8 3/4",
    "-5 32/12 in",
    "-5/7",
    "- 7 3/32",
    "approx. - 9/12",
    "12",
    "Between 1/4 and 3/16th"
]


for string in testStrings {
    print(findFirst(string))
}