From f214f3baa2f3b613f39ded5ac615a887603aa05c Mon Sep 17 00:00:00 2001
From: Eugen Wissner <belka@caraus.de>
Date: Tue, 16 Apr 2019 07:20:52 +0200
Subject: [PATCH] Add algorithm.iteration.foldl

---
 dub.json                           |  2 +-
 encoding/dub.json                  |  2 +-
 meta/dub.json                      |  2 +-
 middle/dub.json                    |  2 +-
 os/dub.json                        |  2 +-
 source/tanya/algorithm/iteration.d | 53 ++++++++++++++++++++++++++++++
 sys/dub.json                       |  2 +-
 test/dub.json                      |  2 +-
 8 files changed, 60 insertions(+), 7 deletions(-)

diff --git a/dub.json b/dub.json
index f0186df..1e1b393 100644
--- a/dub.json
+++ b/dub.json
@@ -79,7 +79,7 @@
 		}
 	],
 
-	"dflags": ["-dip1000"],
+	"dflags-dmd": ["-dip1000"],
 
 	"libs-windows": ["advapi32"],
 	"libs-windows-x86_mscoff": ["iphlpapi"],
diff --git a/encoding/dub.json b/encoding/dub.json
index 441f29d..717656e 100644
--- a/encoding/dub.json
+++ b/encoding/dub.json
@@ -13,5 +13,5 @@
 	"importPaths": [
 		"."
 	],
-	"dflags": ["-dip1000"]
+	"dflags-dmd": ["-dip1000"]
 }
diff --git a/meta/dub.json b/meta/dub.json
index beca5d5..4b7651b 100644
--- a/meta/dub.json
+++ b/meta/dub.json
@@ -9,5 +9,5 @@
 	"importPaths": [
 		"."
 	],
-	"dflags": ["-dip1000"]
+	"dflags-dmd": ["-dip1000"]
 }
diff --git a/middle/dub.json b/middle/dub.json
index f490141..d712f7f 100644
--- a/middle/dub.json
+++ b/middle/dub.json
@@ -19,5 +19,5 @@
 	"importPaths": [
 		"."
 	],
-	"dflags": ["-dip1000"]
+	"dflags-dmd": ["-dip1000"]
 }
diff --git a/os/dub.json b/os/dub.json
index 31537a1..18fe17a 100644
--- a/os/dub.json
+++ b/os/dub.json
@@ -13,5 +13,5 @@
 	"importPaths": [
 		"."
 	],
-	"dflags": ["-dip1000"]
+	"dflags-dmd": ["-dip1000"]
 }
diff --git a/source/tanya/algorithm/iteration.d b/source/tanya/algorithm/iteration.d
index f759e1d..0e91c5d 100644
--- a/source/tanya/algorithm/iteration.d
+++ b/source/tanya/algorithm/iteration.d
@@ -727,3 +727,56 @@ auto singleton(E)(return ref E element)
     singleChar.popFront();
     assert(singleChar.empty);
 }
+
+/**
+ * Accumulates all elements of a range using a function.
+ *
+ * $(D_PSYMBOL foldl) takes a function, an input range and the initial value.
+ * The function takes this initial value and the first element of the range (in
+ * this order), puts them together and returns the result. The return
+ * type of the function should be the same as the type of the initial value.
+ * This is than repeated for all the remaining elements of the range, whereby
+ * the value returned by the passed function is used at the place of the
+ * initial value.
+ *
+ * $(D_PSYMBOL foldl) accumulates from left to right.
+ *
+ * Params:
+ *  F = Callable accepting the accumulator and a range element.
+ */
+template foldl(F...)
+if (F.length == 1)
+{
+    /**
+     * Params:
+     *  R     = Input range type.
+     *  T     = Type of the accumulated value.
+     *  range = Input range.
+     *  init  = Initial value.
+     *
+     * Returns: Accumulated value.
+     */
+    T foldl(R, T)(R range, auto ref T init)
+    if (isInputRange!R && !isInfinite!R)
+    {
+        if (range.empty)
+        {
+            return init;
+        }
+        else
+        {
+            auto acc = F[0](init, range.front);
+            range.popFront;
+            return foldl(range, acc);
+        }
+    }
+}
+
+///
+@nogc nothrow pure @safe unittest
+{
+    int[3] range = [1, 2, 3];
+    const actual = foldl!((acc, x) => acc + x)(range[], 0);
+
+    assert(actual == 6);
+}
diff --git a/sys/dub.json b/sys/dub.json
index 3db3888..9f7099d 100644
--- a/sys/dub.json
+++ b/sys/dub.json
@@ -9,5 +9,5 @@
 	"importPaths": [
 		"."
 	],
-	"dflags": ["-dip1000"]
+	"dflags-dmd": ["-dip1000"]
 }
diff --git a/test/dub.json b/test/dub.json
index e0fc8af..c988bd0 100644
--- a/test/dub.json
+++ b/test/dub.json
@@ -13,5 +13,5 @@
 	"importPaths": [
 		"."
 	],
-	"dflags": ["-dip1000"]
+	"dflags-dmd": ["-dip1000"]
 }