From fac76980fe6e863fcc15023eeeefaa0f1ed6cbd9 Mon Sep 17 00:00:00 2001
From: Justin Ethier <justin.ethier@gmail.com>
Date: Mon, 23 Mar 2015 23:02:26 -0400
Subject: [PATCH] Added (append)

---
 trans.scm | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/trans.scm b/trans.scm
index 8fea0407..692a390b 100644
--- a/trans.scm
+++ b/trans.scm
@@ -70,6 +70,20 @@
       ((pair? obj)
        (list? (cdr obj)))
       (else #f)))
+  ; append accepts a variable number of arguments, per R5RS. So a wrapper
+  ; has been provided for the standard 2-argument version of (append).
+  ;
+  ; We return the given value if less than 2 arguments are given, and
+  ; otherwise fold over each arg, appending it to its predecessor. 
+  (define (append . lst)
+    (define append-2
+            (lambda (inlist alist)
+                    (foldr (lambda (ap in) (cons ap in)) alist inlist)))
+    (if (null? lst)
+        lst
+        (if (null? (cdr lst))
+            (car lst)
+            (foldl (lambda (a b) (append-2 b a)) (car lst) (cdr lst)))))
   (define (list . objs)  objs)
   (define (map func lst)
     (foldr (lambda (x y) (cons (func x) y)) '() lst))