[Swift]extensionで実装するPerl風のsplice() ref: http://qiita.com/worthmine/items/e859e87d6d46355bd069

extensionPerlLikeSplice.swift

extension Array {
    typealias Element = T

    mutating func splice(var _ atIndex :Int = 0, _ length :Int = 0, _ newElements: T...) -> Slice<T>? {
        description
        var theIndex = length + atIndex
        var spliced :Slice<T> = []
        if length < 0 {fatalError("minus length was set")}
        if atIndex >= 0 {
            if theIndex > self.endIndex {fatalError("Bad Access")}
            let preArray = atIndex > 0 ? self[self.startIndex..<atIndex] : []
            spliced = length > 0 ? self[atIndex..<theIndex] : []
            let postArray = self[theIndex..<self.endIndex]
            self = preArray + Array(newElements) + postArray
            return length > 0 ? Slice(spliced) : nil
        } else {    // you can use minus atIndex because it is like Perl
            let reversed = self.reverse()
            atIndex = abs(atIndex + 1)
            theIndex = length + atIndex
            if theIndex > self.endIndex {fatalError("Bad Access")}
            let postArray = atIndex > 0 ? reversed[reversed.startIndex..<atIndex].reverse() : []
            spliced = length > 0 ? reversed[atIndex..<theIndex].reverse() : []
            let preArray =   theIndex < reversed.endIndex ? reversed[theIndex..<reversed.endIndex].reverse() :[]
            self = preArray + Array(newElements) + postArray
            return length > 0 ? Slice(spliced) : nil
        }
    }
}

file2.txt

a.splice(-1, 0, "push" )    // push()
a.splice(-1, 1 )            // pop()
a.splice(0, 0, "unshift" )  // unshift()
a.splice(0, 1)              // shift()

file3.txt

a   // -> ["Four", "Five", "Six", "Seven", "Eight"]
a.splice(0, a.count, "other", "Strings", "like", "those")
a   // -> ["other", "Strings", "like", "those"]

file4.txt

a.splice(-2, 2)             // -> ["Strings", "like"]

file5.txt

a = ["Four", "Seven", "Eight" ]
a.splice(["Five", "Six"], atIndex: 1)   // using a default splice
a.splice(2, 2, "Six2", "Seven2")        // -> {["Seven", "Eight"]} // using mutating splice
a.splice(0, 1)　                        // -> {[“Four"]}

useDefaultSplice.swift

var a :Array = ["Four", "Seven", "Eight" ]
a.splice(["Five", "Six"], atIndex: 1)    // -> ["Four","Five","Six",”Seven”,”Eight"]