From 71917d501c8fb8c117766aef0277fdee6af6ce91 Mon Sep 17 00:00:00 2001
From: Cameron Ross <elpenguino@gmail.com>
Date: Wed, 16 Jan 2019 00:57:38 -0330
Subject: [PATCH] let Queue be a range (#220)

let Queue be a range
merged-on-behalf-of: BBasile <BBasile@users.noreply.github.com>
---
 source/dyaml/emitter.d |  8 +-------
 source/dyaml/queue.d   | 44 +++++++++++++++++++-----------------------
 2 files changed, 21 insertions(+), 31 deletions(-)

diff --git a/source/dyaml/emitter.d b/source/dyaml/emitter.d
index 8eef1c3..cd74507 100644
--- a/source/dyaml/emitter.d
+++ b/source/dyaml/emitter.d
@@ -273,14 +273,8 @@ struct Emitter(Range, CharType) if (isOutputRange!(Range, CharType))
         {
             int level;
 
-            //Rather ugly, but good enough for now.
-            //Couldn't be bothered writing a range as events_ should eventually
-            //become a Phobos queue/linked list.
-            events_.startIteration();
-            events_.next();
-            while(!events_.iterationOver())
+            foreach(const event; events_.range)
             {
-                const event = events_.next();
                 static starts = [EventID.documentStart, EventID.sequenceStart, EventID.mappingStart];
                 static ends   = [EventID.documentEnd, EventID.sequenceEnd, EventID.mappingEnd];
                 if(starts.canFind(event.id))   {++level;}
diff --git a/source/dyaml/queue.d b/source/dyaml/queue.d
index 710bd39..57b0d34 100644
--- a/source/dyaml/queue.d
+++ b/source/dyaml/queue.d
@@ -36,8 +36,6 @@ private:
     Node* first_;
     // Last element of the linked list - last element added in time (start of the queue).
     Node* last_;
-    // Cursor pointing to the current node in iteration.
-    Node* cursor_;
     // free-list
     Node* stock;
 
@@ -119,30 +117,28 @@ public:
         freeStock();
     }
 
-    /// Start iterating over the queue.
-    void startIteration() @safe pure nothrow @nogc
+    /// Returns a forward range iterating over this queue.
+    auto range() @safe pure nothrow @nogc
     {
-        cursor_ = first_;
-    }
+        static struct Result
+        {
+            private Node* cursor;
 
-    /// Returns: The next element in the queue.
-    ref const(T) next() @safe pure nothrow @nogc
-    in
-    {
-        assert(!empty);
-        assert(cursor_ !is null);
-    }
-    do
-    {
-        const previous = cursor_;
-        cursor_ = cursor_.next_;
-        return previous.payload_;
-    }
-
-    /// Returns: true if itrating is not possible anymore, false otherwise.
-    bool iterationOver() @safe pure nothrow const @nogc
-    {
-        return cursor_ is null;
+            void popFront() @safe pure nothrow @nogc
+            {
+                cursor = cursor.next_;
+            }
+            ref T front() @safe pure nothrow @nogc
+            in(cursor !is null)
+            {
+                return cursor.payload_;
+            }
+            bool empty() @safe pure nothrow @nogc const
+            {
+                return cursor is null;
+            }
+        }
+        return Result(first_);
     }
 
     /// Push a new item to the queue.