Haskell style find for Swift Sliceable collections.

SwiftFind.swift

func find<S : Sliceable>(domain: S, isValue: (S.Generator.Element) -> Bool) -> S.Index? {
    return find(domain, domain.startIndex, isValue)
}
func find<S : Sliceable>(domain: S, startingIndex: S.Index, isValue: (S.Generator.Element) -> Bool) -> S.Index? {
    if startingIndex == domain.endIndex {
        return nil
    }
    if isValue(domain[startingIndex]) {
        return startingIndex
    }
    return find(domain, startingIndex.successor(), isValue)
}

/**
Usage

let origRanges: [HalfOpenInterval<Float>] = [0..<2, 2..<4, 4..<6]
let rIndex = find(origRanges) {
    $0 ~= 2.5
}
if let ri = rIndex {
    println(origRanges[rIndex])  // 2.0..<4.0
}
*/