From 834b0019a715f6351d53963f743361651cd60912 Mon Sep 17 00:00:00 2001
From: Matthew Wampler-Doty <matt@w-d.org>
Date: Mon, 21 Apr 2014 12:35:56 -0700
Subject: [PATCH] Fixing `doto` to be API compatible with Clojure's `doto`

---
 docs/language/api.rst      | 22 ++++++++++------------
 hy/core/macros.hy          | 17 +++++++++--------
 tests/native_tests/core.hy |  6 +++++-
 3 files changed, 24 insertions(+), 21 deletions(-)

diff --git a/docs/language/api.rst b/docs/language/api.rst
index f5b1ac5..53b89a5 100644
--- a/docs/language/api.rst
+++ b/docs/language/api.rst
@@ -563,23 +563,21 @@ del
 doto
 ----
 
-`doto` macro is used to make repetitive calls to an object easy. Following
-example demonstrates this.
+`doto` macro is used to make a sequence of method calls for an object easy.
+
+.. code-block:: clj
+
+  => (doto [] (.append 1) (.append 2) .reverse)
+  [2 1]
 
 .. code-block:: clj
 
   => (setv collection [])
-  => (doto collection (.append 1) (.append 2))
+  => (.append collection 1)
+  => (.append collection 2)
+  => (.reverse collection)
   => collection
-  [1 2]
-
-.. code-block:: clj
-
-  => (setv collection [])
-  => (.append 1 collection)
-  => (.append 2 collection)
-  => collection
-  [1 2]
+  [2 1]
 
 eval
 ----
diff --git a/hy/core/macros.hy b/hy/core/macros.hy
index 548a81b..29db215 100644
--- a/hy/core/macros.hy
+++ b/hy/core/macros.hy
@@ -128,14 +128,15 @@
 
 
 (defmacro doto [form &rest expressions]
-  (setv expressions (iter expressions))
-  (defn build-form [form expression]
-    `(~(first expression) ~form ~@(rest expression)))
-  (setv result `())
-  (for* [expression expressions]
-    (.append result (build-form form expression)))
-  `(do ~@result))
-
+  "Performs a sequence of potentially mutating actions on an initial object, returning the resulting object after the sequence is performed"
+  (setv f (gensym))
+  (defn build-form [expression]
+    (if (isinstance expression HyExpression)
+      `(~(first expression) ~f ~@(rest expression))
+      `(~expression ~f)))
+  `(let [[~f ~form]]
+     ~@(map build-form expressions)
+     ~f))
 
 (defmacro ->> [head &rest rest]
   ;; TODO: fix the docstring by someone who understands this
diff --git a/tests/native_tests/core.hy b/tests/native_tests/core.hy
index fec1316..c1ef191 100644
--- a/tests/native_tests/core.hy
+++ b/tests/native_tests/core.hy
@@ -483,5 +483,9 @@
   "NATIVE: testing doto macro"
   (setv collection [])
   (doto collection (.append 1) (.append 2) (.append 3))
-  (assert-equal collection [1 2 3]))
+  (assert-equal collection [1 2 3])
+  (setv res (doto (set) (.add 2) (.add 1)))
+  (assert-equal res (set [1 2]))
+  (setv res (doto [] (.append 1) (.append 2) .reverse))
+  (assert-equal res [2 1]))