Elvis Operator.swift

infix operator ?|: NilCoalescingPrecedence

extension Collection {
	/** Elvis Operator (`?:` or `||` in other languages)
	Works on String, Array, Collection, Set, etc.
	Returns the left-hand value if it is not empty.
	
	    "" ?| "Default"       // "Default"
	    "String" ?| "Default" // "String"
	    
	    0 ?| 4	              // 4
	    1 ?| 4	              // 1
	    -1 ?| 4	              // -1
	    
	    [] ?| [7,8]           // [7,8]
	    [1,2] ?| [7,8]        // [1,2]
	*/
	public static func ?| (lhs: Self, rhs: @autoclosure () throws -> Self) rethrows -> Self {
		!lhs.isEmpty ? lhs : try rhs()
    }
}

extension BinaryInteger {
	/// Elvis Operator (`?:` or `||` in other languages)
	/// Returns the left-hand value if it is not 0.
	public static func ?| (lhs: Self, rhs: @autoclosure () throws -> Self) rethrows -> Self {
		lhs != 0 ? lhs : try rhs()
    }
}