From 76bda0ac8df2f9e5d49e126d16d785f5c63c4430 Mon Sep 17 00:00:00 2001
From: Eugen Wissner <belka@caraus.de>
Date: Wed, 17 Apr 2019 06:27:18 +0200
Subject: [PATCH] Add getAndPopFront()/getAndPopBack()

---
 source/tanya/algorithm/iteration.d |  5 +-
 source/tanya/container/array.d     |  8 +--
 source/tanya/range/primitive.d     | 94 ++++++++++++++++++++++++++++++
 3 files changed, 98 insertions(+), 9 deletions(-)

diff --git a/source/tanya/algorithm/iteration.d b/source/tanya/algorithm/iteration.d
index 0e91c5d..e71d581 100644
--- a/source/tanya/algorithm/iteration.d
+++ b/source/tanya/algorithm/iteration.d
@@ -756,7 +756,7 @@ if (F.length == 1)
      *
      * Returns: Accumulated value.
      */
-    T foldl(R, T)(R range, auto ref T init)
+    auto foldl(R, T)(R range, auto ref T init)
     if (isInputRange!R && !isInfinite!R)
     {
         if (range.empty)
@@ -765,8 +765,7 @@ if (F.length == 1)
         }
         else
         {
-            auto acc = F[0](init, range.front);
-            range.popFront;
+            auto acc = F[0](init, getAndPopFront(range));
             return foldl(range, acc);
         }
     }
diff --git a/source/tanya/container/array.d b/source/tanya/container/array.d
index 5b3f522..872d55e 100644
--- a/source/tanya/container/array.d
+++ b/source/tanya/container/array.d
@@ -16,6 +16,7 @@ module tanya.container.array;
 
 import core.checkedint;
 import tanya.algorithm.comparison;
+import tanya.algorithm.iteration;
 import tanya.algorithm.mutation;
 import tanya.memory.allocator;
 import tanya.memory.lifetime;
@@ -670,12 +671,7 @@ struct Array(T)
         {
             reserve(length + el.length);
         }
-        size_t retLength;
-        foreach (e; el)
-        {
-            retLength += insertBack(e);
-        }
-        return retLength;
+        return foldl!((acc, e) => acc + insertBack(e))(el, 0U);
     }
 
     /// ditto
diff --git a/source/tanya/range/primitive.d b/source/tanya/range/primitive.d
index 82950ac..258d5d5 100644
--- a/source/tanya/range/primitive.d
+++ b/source/tanya/range/primitive.d
@@ -1545,3 +1545,97 @@ if (isInputRange!Range && hasLvalueElements!Range)
 
     assert(!sameHead(r1, r2));
 }
+
+/**
+ * Returns the first element and advances the range.
+ *
+ * If $(D_PARAM range) has lvalue elements, then $(D_PSYMBOL getAndPopFront)
+ * returns by reference, otherwise the returned element is copied.
+ *
+ * Params:
+ *  R     = Input range type.
+ *  range = Input range.
+ *
+ * Returns: Front range element.
+ *
+ * See_Also: $(D_PSYMBOL getAndPopBack).
+ */
+ElementType!R getAndPopFront(R)(ref R range)
+if (isInputRange!R)
+in (!range.empty)
+{
+    static if (hasLvalueElements!R)
+    {
+        auto el = (() @trusted => &range.front())();
+    }
+    else
+    {
+        auto el = range.front;
+    }
+    range.popFront();
+    static if (hasLvalueElements!R)
+    {
+        return *el;
+    }
+    else
+    {
+        return el;
+    }
+}
+
+///
+@nogc nothrow pure @safe unittest
+{
+    int[3] array = [1, 2, 3];
+    auto slice = array[];
+
+    assert(getAndPopFront(slice) == 1);
+    assert(slice.length == 2);
+}
+
+/**
+ * Returns the last element and removes it from the range.
+ *
+ * If $(D_PARAM range) has lvalue elements, then $(D_PSYMBOL getAndPopBack)
+ * returns by reference, otherwise the returned element is copied.
+ *
+ * Params:
+ *  R     = Bidirectional range type.
+ *  range = Bidirectional range.
+ *
+ * Returns: Last range element.
+ *
+ * See_Also: $(D_PSYMBOL getAndPopFront).
+ */
+auto ref getAndPopBack(R)(ref R range)
+if (isBidirectionalRange!R)
+in (!range.empty)
+{
+    static if (hasLvalueElements!R)
+    {
+        auto el = (() @trusted => &range.back())();
+    }
+    else
+    {
+        auto el = range.back;
+    }
+    range.popBack();
+    static if (hasLvalueElements!R)
+    {
+        return *el;
+    }
+    else
+    {
+        return el;
+    }
+}
+
+///
+@nogc nothrow pure @trusted unittest
+{
+    int[3] array = [1, 2, 3];
+    auto slice = array[];
+
+    assert(getAndPopBack(slice) == 3);
+    assert(slice.length == 2);
+}