lazierdestructuring.diff

From 11d0bc951403f823df65c9d00fd4766873c65311 Mon Sep 17 00:00:00 2001
From: Achim Passen <achim.passen@gmail.com>
Date: Wed, 1 Jul 2009 03:45:44 +0200
Subject: [PATCH] Added [x &rest xs] binding form for lazier destructuring, added nthrest to core

---
 src/clj/clojure/core.clj |    9 +++++++++
 1 files changed, 9 insertions(+), 0 deletions(-)

diff --git a/src/clj/clojure/core.clj b/src/clj/clojure/core.clj
index 38c58da..8adfb4c 100644
--- a/src/clj/clojure/core.clj
+++ b/src/clj/clojure/core.clj
@@ -2574,6 +2574,11 @@
         (recur (dec n) (next xs))
         xs)))
 
+(defn nthrest
+  "Returns the nth next of coll, coll when n is 0."
+  [coll n]
+  (nth (iterate rest coll) n))
+
 
 ;redefine let and loop  with destructuring
 (defn destructure [bindings]
@@ -2593,6 +2598,10 @@
                                                      n
                                                      (nnext bs)
                                                      true)
+                                (= firstb '&rest) (recur (pb ret (second bs) (list `nthrest gvec n))
+                                                         n
+                                                         (nnext bs)
+                                                         true)
                                 (= firstb :as) (pb ret (second bs) gvec)
                                 :else (if seen-rest?
                                         (throw (new Exception "Unsupported binding form, only :as can follow & parameter"))
-- 
1.6.3.3