Lift/const operator in Swift

LiftOperator.swift

/// Lift operator (instance to function, function to function with one more parameter, key-path to function)
/// This operator is similar to `const` function from Haskell.
prefix operator ^

/// Lift instance to function returning constant result.
@inline(__always)
prefix func ^ <T>(instance: @autoclosure @escaping () -> T) -> () -> T {
    return instance
}

/// Lift function with no parameters to function with one parameter,
/// which will be thrown-away.
@inline(__always)
prefix func ^ <P, R>(function: @escaping () -> R) -> (P) -> R {
    return { _ in
        function()
    }
}

/// Lift key-path to function receiving instance and returning property value.
@inline(__always)
prefix func ^ <T, P>(keyPath: KeyPath<T, P>) -> (T) -> P {
    return { $0[keyPath: keyPath] }
}