From 6e00b931a9df9c98f6441b3b11f946409c7c2cd8 Mon Sep 17 00:00:00 2001
From: Stuart Halloway <stu@thinkrelevance.com>
Date: Tue, 12 Jul 2011 08:23:43 -0500
Subject: [PATCH] scopes spike

---
 src/clj/clojure/core.clj |   65 +++++++++++++++++++++++++++++++++++----------
 src/clj/clojure/main.clj |   15 +++++-----
 2 files changed, 58 insertions(+), 22 deletions(-)

diff --git a/src/clj/clojure/core.clj b/src/clj/clojure/core.clj
index 851df37..7941308 100644
--- a/src/clj/clojure/core.clj
+++ b/src/clj/clojure/core.clj
@@ -3351,26 +3351,61 @@
   ([v start end]
    (. clojure.lang.RT (subvec v start end))))
 
+(def ^:dynamic *scope*)
+
+(defn ^:private cleanup-scope
+  "Explicitly close the resources bound to the current scope.
+   Not normally called from user code."
+  []
+  (when-let [^Closeable c (peek @*scope*)]
+    (if (instance? java.io.Closeable c)
+      (.close ^java.io.Closeable c)
+      (c))
+    (swap! *scope* pop)
+    (recur)))
+
+(defmacro with-scope
+  "Create a new scope and run the forms in body. In a finally
+   block, close any resources added to the scope."
+  {:added "1.3"}
+  [& body]
+  `(binding [*scope* (atom nil)]
+     (try
+      ~@body
+      (finally
+       (@#'cleanup-scope)))))
+
+(defn scope
+  "Fluent interface to add c to the current scope.
+   c can be a java.io.Closeable or an arbitrary fn
+   of one argument."
+  {:added "1.3"}
+  [c]
+  (swap! *scope* conj c)
+  c)
+
 (defmacro with-open
   "bindings => [name init ...]
 
-  Evaluates body in a try expression with names bound to the values
-  of the inits, and a finally clause that calls (.close name) on each
-  name in reverse order."
+   Evaluates body with names bound to the values of the inits.
+   Values should be instances of java.io.Closeable or
+   zero-arg fns. Each value is added to the current scope.
+   Calls cleanup-scope from a finally block protecting body."
   {:added "1.0"}
   [bindings & body]
-  (assert-args with-open
-     (vector? bindings) "a vector for its binding"
-     (even? (count bindings)) "an even number of forms in binding vector")
-  (cond
-    (= (count bindings) 0) `(do ~@body)
-    (symbol? (bindings 0)) `(let ~(subvec bindings 0 2)
-                              (try
-                                (with-open ~(subvec bindings 2) ~@body)
-                                (finally
-                                  (. ~(bindings 0) close))))
-    :else (throw (IllegalArgumentException.
-                   "with-open only allows Symbols in bindings"))))
+  (let [helper (fn helper [bindings body]
+                 (cond
+                  (= (count bindings) 0) `(do ~@body)
+                  (symbol? (bindings 0)) `(let ~(subvec bindings 0 2)
+                                            (do
+                                              (swap! *scope* conj ~(bindings 0))
+                                              ~(helper (subvec bindings 2) body)))))]
+    (cond
+     (= (count bindings) 0) `(do ~@body)
+     (symbol? (bindings 0)) `(with-scope
+                               ~(helper bindings body))
+     :else (throw (IllegalArgumentException.
+                   "scoped only allows symbols in bindings")))))
 
 (defmacro doto
   "Evaluates x then calls all of the methods and functions with the
diff --git a/src/clj/clojure/main.clj b/src/clj/clojure/main.clj
index 5598daf..1b34e81 100644
--- a/src/clj/clojure/main.clj
+++ b/src/clj/clojure/main.clj
@@ -239,13 +239,14 @@
         read-eval-print
         (fn []
           (try
-           (let [input (read request-prompt request-exit)]
-             (or (#{request-prompt request-exit} input)
-                 (let [value (eval input)]
-                   (print value)
-                   (set! *3 *2)
-                   (set! *2 *1)
-                   (set! *1 value))))
+           (with-scope
+             (let [input (read request-prompt request-exit)]
+               (or (#{request-prompt request-exit} input)
+                   (let [value (eval input)]
+                     (print value)
+                     (set! *3 *2)
+                     (set! *2 *1)
+                     (set! *1 value)))))
            (catch Throwable e
              (caught e)
              (set! *e e))))]
-- 
1.7.3.5