fixed bug851

added "Function" module to library/scala

1 files changed, 118 insertions, 0 deletions

diff --git a/src/library/scala/Function.scala b/src/library/scala/Function.scala
new file mode 100644
index 0000000000..7e6e29b0f0
--- /dev/null
+++ b/src/library/scala/Function.scala
@@ -0,0 +1,118 @@
+package scala
+
+/** A module defining utility methods for higher-order functional programming.
+ */
+object Function extends Application {
+
+  /** 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)) }
+
+  /** Currying for functions of arity 2. This transforms a function
+   *  of arity 2 into a a unary function returning another unary function.
+   */
+  def curried[a1, a2, b](f: (a1, a2) => b): a1 => a2 => b  =  {
+    x1 => x2 => f(x1, x2)
+  }
+
+  /** Currying for functions of arity 3.
+   */
+  def curried[a1, a2, a3, b](f: (a1, a2, a3) => b): a1 => a2 => a3 => b  =  {
+    x1 => x2 => x3 => f(x1, x2, x3)
+  }
+
+  /** Currying for functions of arity 4.
+   */
+  def curried[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)
+  }
+
+  /** Currying for functions of arity 5.
+   */
+  def curried[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)
+  }
+
+  /** 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.
+   */
+  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.
+   */
+  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.
+   */
+  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.
+   */
+  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))
+  }
+}