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Standard library for the Scala Programming Language
/* __ *\
** ________ ___ / / ___ Scala API **
** / __/ __// _ | / / / _ | (c) 2003-2013, LAMP/EPFL **
** __\ \/ /__/ __ |/ /__/ __ | http://scala-lang.org/ **
** /____/\___/_/ |_/____/_/ | | **
** |/ **
\* */
package scala
/** A module defining utility methods for higher-order functional programming.
*
* @author Martin Odersky
* @version 1.0, 29/11/2006
*/
object Function {
/** Given a sequence of functions `f,,1,,`, ..., `f,,n,,`, return the
* function `f,,1,, andThen ... andThen f,,n,,`.
*
* @param fs The given sequence of functions
*/
def chain[a](fs: Seq[a => a]): a => a = { x => (x /: fs) ((x, f) => f(x)) }
/** The constant function */
def const[T, U](x: T)(y: U): T = x
/** Turns a function `A => Option[B]` into a `PartialFunction[A, B]`.
*
* '''Important note''': this transformation implies the original function
* may be called 2 or more times on each logical invocation, because the
* only way to supply an implementation of `isDefinedAt` is to call the
* function and examine the return value.
* See also [[scala.PartialFunction]], method `applyOrElse`.
*
* @param f a function `T => Option[R]`
* @return a partial function defined for those inputs where
* f returns `Some(_)` and undefined where `f` returns `None`.
* @see [[scala.PartialFunction]], method `lift`.
*/
def unlift[T, R](f: T => Option[R]): PartialFunction[T, R] = PartialFunction.unlifted(f)
/** Uncurrying for functions of arity 2. This transforms a unary function
* returning another unary function into a function of arity 2.
*/
def uncurried[a1, a2, b](f: a1 => a2 => b): (a1, a2) => b = {
(x1, x2) => f(x1)(x2)
}
/** Uncurrying for functions of arity 3.
*/
def uncurried[a1, a2, a3, b](f: a1 => a2 => a3 => b): (a1, a2, a3) => b = {
(x1, x2, x3) => f(x1)(x2)(x3)
}
/** Uncurrying for functions of arity 4.
*/
def uncurried[a1, a2, a3, a4, b](f: a1 => a2 => a3 => a4 => b): (a1, a2, a3, a4) => b = {
(x1, x2, x3, x4) => f(x1)(x2)(x3)(x4)
}
/** Uncurrying for functions of arity 5.
*/
def uncurried[a1, a2, a3, a4, a5, b](f: a1 => a2 => a3 => a4 => a5 => b): (a1, a2, a3, a4, a5) => b = {
(x1, x2, x3, x4, x5) => f(x1)(x2)(x3)(x4)(x5)
}
/** Tupling for functions of arity 2. This transforms a function
* of arity 2 into a unary function that takes a pair of arguments.
*
* @note These functions are slotted for deprecation, but it is on
* hold pending superior type inference for tupling anonymous functions.
*/
// @deprecated("use `f.tupled` instead")
def tupled[a1, a2, b](f: (a1, a2) => b): Tuple2[a1, a2] => b = {
case Tuple2(x1, x2) => f(x1, x2)
}
/** Tupling for functions of arity 3. This transforms a function
* of arity 3 into a unary function that takes a triple of arguments.
*/
// @deprecated("use `f.tupled` instead")
def tupled[a1, a2, a3, b](f: (a1, a2, a3) => b): Tuple3[a1, a2, a3] => b = {
case Tuple3(x1, x2, x3) => f(x1, x2, x3)
}
/** Tupling for functions of arity 4. This transforms a function
* of arity 4 into a unary function that takes a 4-tuple of arguments.
*/
// @deprecated("use `f.tupled` instead")
def tupled[a1, a2, a3, a4, b](f: (a1, a2, a3, a4) => b): Tuple4[a1, a2, a3, a4] => b = {
case Tuple4(x1, x2, x3, x4) => f(x1, x2, x3, x4)
}
/** Tupling for functions of arity 5. This transforms a function
* of arity 5 into a unary function that takes a 5-tuple of arguments.
*/
// @deprecated("use `f.tupled` instead")
def tupled[a1, a2, a3, a4, a5, b](f: (a1, a2, a3, a4, a5) => b): Tuple5[a1, a2, a3, a4, a5] => b = {
case Tuple5(x1, x2, x3, x4, x5) => f(x1, x2, x3, x4, x5)
}
/** Un-tupling for functions of arity 2. This transforms a function taking
* a pair of arguments into a binary function which takes each argument separately.
*/
def untupled[a1, a2, b](f: Tuple2[a1, a2] => b): (a1, a2) => b = {
(x1, x2) => f(Tuple2(x1, x2))
}
/** Un-tupling for functions of arity 3. This transforms a function taking
* a triple of arguments into a ternary function which takes each argument separately.
*/
def untupled[a1, a2, a3, b](f: Tuple3[a1, a2, a3] => b): (a1, a2, a3) => b = {
(x1, x2, x3) => f(Tuple3(x1, x2, x3))
}
/** Un-tupling for functions of arity 4. This transforms a function taking
* a 4-tuple of arguments into a function of arity 4 which takes each argument separately.
*/
def untupled[a1, a2, a3, a4, b](f: Tuple4[a1, a2, a3, a4] => b): (a1, a2, a3, a4) => b = {
(x1, x2, x3, x4) => f(Tuple4(x1, x2, x3, x4))
}
/** Un-tupling for functions of arity 5. This transforms a function taking
* a 5-tuple of arguments into a function of arity 5 which takes each argument separately.
*/
def untupled[a1, a2, a3, a4, a5, b](f: Tuple5[a1, a2, a3, a4, a5] => b): (a1, a2, a3, a4, a5) => b = {
(x1, x2, x3, x4, x5) => f(Tuple5(x1, x2, x3, x4, x5))
}
}