Swift.Set extensions

Set+TJU.swift

//
//  Set.swift
//  TonalKit
//
//  Created by TJ Usiyan on 3/2/15.
//  Copyright (c) 2015 buttons-and-lights. All rights reserved.
//  https://gist.github.com/17d2f63780e9549a3335.git

import Foundation

extension Set {
    func reduce<U>(initial: U, @noescape combine: (U, T) -> U) -> U {
        return Swift.reduce(self, initial, combine)
    }

    func filter(includeElement: (T) -> Bool) -> Set {
        return reduce(Set()) { includeElement($1) ? $0.union($1) : $0 }
    }

    func map<U>(transform: (T) -> U) -> Set<U> {
        return reduce(Set<U>()) { $0.union(transform($1)) }
    }
}

extension Set {
    func union(items: T ...) -> Set {
        return union(items)
    }
}

extension Set {
    func mapSome<U>(transform: (T) -> U?) -> Set<U> {
        var result = Set<U>()
        for x in self {
            if let y = transform(x) {
                result.unionInPlace([y]) /* @todo rdar inability to append 2015-03-15 */
            }
        }
        return result
    }
}