RangeReplaceableCollectionType.swift

extension RangeReplaceableCollectionType {
    init<S: SequenceType where S.Generator.Element == Self.Generator.Element>(sequence: S) {
        self.init()
        extend(sequence)
    }
}

extension RangeReplaceableCollectionType where Index: IntegerType {
    init<S: SequenceType where S.Generator.Element == Self.Generator.Element>(sequence: S) {
        self.init()
        self.reserveCapacity(numericCast(sequence.underestimateCount()))
        self.extend(sequence)
    }
}

extension Dictionary: RangeReplaceableCollectionType {
    public mutating func replaceRange<C : CollectionType where C.Generator.Element == Generator.Element>(subRange: Range<Index>, with newElements: C) {
        for index in subRange {
            removeAtIndex(index)
        }

        extend(newElements)
    }

    public mutating func reserveCapacity(n: Index.Distance) {}

    public mutating func append(newElement: Generator.Element) {
        let (key, value) = newElement
        self[key] = value
    }

    public mutating func extend<S : SequenceType where S.Generator.Element == Generator.Element>(newElements: S) {
        for newElement in newElements {
            append(newElement)
        }
    }

    public mutating func insert(newElement: Generator.Element, atIndex i: Index) {
        append(newElement)
    }

    public mutating func splice<C : CollectionType where C.Generator.Element == Generator.Element>(newElements: C, atIndex i: Index) {
        extend(newElements)
    }

    public mutating func removeRange(subRange: Range<Index>) {
        for index in subRange {
            removeAtIndex(index)
        }
    }
}