Added bound-fn to define thread-local binding aware functions

bound-fn captures the thread-local bindings in effect where the
function is defined. Installs these bindings before executing the
body. This is useful for helper functions running in a different
thread.

Excluded with-bindings from clojure/main.clj to prevent name clash.

Fixes #170

Signed-off-by: Chouser <chouser@n01se.net>

src/clj/clojure/core.clj

@@ -1253,6 +1253,42 @@
          (finally
            (pop-thread-bindings))))))
 
+(defn with-bindings*
+  "Takes a map of Var/value pairs. Installs for the given Vars the associated
+  values as thread-local bindings. Then calls f with the supplied arguments.
+  Pops the installed bindings after f returned. Returns whatever f returns."
+  [binding-map f & args]
+  (push-thread-bindings binding-map)
+  (try
+    (apply f args)
+    (finally
+      (pop-thread-bindings))))
+
+(defmacro with-bindings
+  "Takes a map of Var/value pairs. Installs for the given Vars the associated
+  values as thread-local bindings. The executes body. Pops the installed
+  bindings after body was evaluated. Returns the value of body."
+  [binding-map & body]
+  `(with-bindings* ~binding-map (fn [] ~@body)))
+
+(defn bound-fn*
+  "Returns a function, which will install the same bindings in effect as in
+  the thread at the time bound-fn* was called and then call f with any given
+  arguments. This may be used to define a helper function which runs on a
+  different thread, but needs the same bindings in place."
+  [f]
+  (let [bindings (get-thread-bindings)]
+    (fn [& args]
+      (apply with-bindings* bindings f args))))
+
+(defmacro bound-fn
+  "Returns a function defined by the given fntail, which will install the
+  same bindings in effect as in the thread at the time bound-fn was called.
+  This may be used to define a helper function which runs on a different
+  thread, but needs the same bindings in place."
+  [& fntail]
+  `(bound-fn* (fn ~@fntail)))
+
 (defn find-var
   "Returns the global var named by the namespace-qualified symbol, or
   nil if no var with that name."

src/clj/clojure/main.clj

@@ -9,6 +9,7 @@
 ;; Originally contributed by Stephen C. Gilardi
 
 (ns clojure.main
+  (:refer-clojure :exclude [with-bindings])
   (:import (clojure.lang Compiler Compiler$CompilerException
                          LineNumberingPushbackReader RT)))