From a94b1b0af46f69216b6c78ced37de80dc2ffae24 Mon Sep 17 00:00:00 2001
From: Eugen Wissner <belka@caraus.de>
Date: Sat, 7 Jul 2018 12:17:59 +0200
Subject: [PATCH] Add functional module. Fix #52

---
 .travis.yml               |  3 +-
 README.md                 |  5 ++-
 appveyor.yml              |  6 ++++
 source/tanya/functional.d | 71 +++++++++++++++++++++++++++++++++++++++
 4 files changed, 83 insertions(+), 2 deletions(-)
 create mode 100644 source/tanya/functional.d

diff --git a/.travis.yml b/.travis.yml
index b0cb77f..20b547d 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -7,6 +7,7 @@ os:
 language: d
 
 d:
+  - dmd-2.081.0
   - dmd-2.080.1
   - dmd-2.079.1
   - dmd-2.078.3
@@ -23,7 +24,7 @@ addons:
       - gcc-multilib
 
 before_script:
-  - if [ "`$DC --version | head -n 1 | grep 'v2.080.1'`" ]; then
+  - if [ "`$DC --version | head -n 1 | grep 'v2.081.0'`" ]; then
       export UNITTEST="unittest-cov";
     fi
 
diff --git a/README.md b/README.md
index a6867ab..dbf2109 100644
--- a/README.md
+++ b/README.md
@@ -32,6 +32,8 @@ types.
 * `encoding`: This package provides tools to work with text encodings.
 * `exception`: Common exceptions and errors.
 * `format`: Formatting and conversion functions.
+* `functional`: Functions that manipulate other functions and their argument
+lists.
 * `hash`: Hash algorithms.
 * `math`: Arbitrary precision integer and a set of functions.
 * `memory`: Tools for manual memory management (allocators, smart pointers).
@@ -172,7 +174,8 @@ parameter is used)
 
 | DMD     | GCC       |
 |:-------:|:---------:|
-| 2.080.1 | *master*  |
+| 2.081.0 | *master*  |
+| 2.080.1 |           |
 | 2.079.1 |           |
 | 2.078.3 |           |
 | 2.077.1 |           |
diff --git a/appveyor.yml b/appveyor.yml
index 7d10c0b..2da2d02 100644
--- a/appveyor.yml
+++ b/appveyor.yml
@@ -3,6 +3,12 @@ os: Visual Studio 2015
 
 environment:
   matrix:
+    - DC: dmd
+      DVersion: 2.081.0
+      arch: x64
+    - DC: dmd
+      DVersion: 2.081.0
+      arch: x86
     - DC: dmd
       DVersion: 2.080.1
       arch: x64
diff --git a/source/tanya/functional.d b/source/tanya/functional.d
new file mode 100644
index 0000000..3b5adf5
--- /dev/null
+++ b/source/tanya/functional.d
@@ -0,0 +1,71 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/**
+ * Functions that manipulate other functions and their argument lists.
+ *
+ * Copyright: Eugene Wissner 2018.
+ * License: $(LINK2 https://www.mozilla.org/en-US/MPL/2.0/,
+ *                  Mozilla Public License, v. 2.0).
+ * Authors: $(LINK2 mailto:info@caraus.de, Eugene Wissner)
+ * Source: $(LINK2 https://github.com/caraus-ecms/tanya/blob/master/source/tanya/functional.d,
+ *                 tanya/functional.d)
+ */
+module tanya.functional;
+
+import tanya.algorithm.mutation;
+import tanya.meta.metafunction;
+
+private template forwardOne(alias arg)
+{
+    static if (__traits(isRef, arg) || __traits(isOut, arg))
+    {
+        alias forwardOne = arg;
+    }
+    else
+    {
+        @property auto forwardOne()
+        {
+            return move(arg);
+        }
+    }
+}
+
+/**
+ * Forwards its argument list preserving $(D_KEYWORD ref) and $(D_KEYWORD out)
+ * storage classes.
+ *
+ * $(D_PSYMBOL forward) accepts a list of variables or literals. It returns an
+ * argument list of the same length that can be for example passed to a
+ * function accepting the arguments of this type.
+ *
+ * Params:
+ *  args = Argument list.
+ *
+ * Returns: $(D_PARAM args) with their original storage classes.
+ */
+template forward(args...)
+{
+    static if (args.length == 1)
+    {
+        alias forward = forwardOne!(args[0]);
+    }
+    else
+    {
+        alias forward = Map!(forwardOne, args);
+    }
+}
+
+///
+@nogc nothrow pure @safe unittest
+{
+    static assert(is(typeof((int i) { int v = forward!i; })));
+    static assert(is(typeof((ref int i) { int v = forward!i; })));
+    static assert(is(typeof({
+        void f(int i, ref int j, out int k)
+        {
+            f(forward!(i, j, k));
+        }
+    })));
+}