added scrambler example

2 files changed, 31 insertions, 1 deletions

diff --git a/README.md b/README.md
index 86c9c49..4f455f7 100644
--- a/README.md
+++ b/README.md
@@ -87,6 +87,36 @@ example apears at the end of the document, following the tutorial.
 
 ```
 
+### A Silly Scrambler
+
+``` lisp 
+
+;; see examples.lisp for defuns of PAD and CHUNK
+
+> (defun scramble (n str)
+    (assert (< n (length str)))
+    (let ((str (pad str (* n (ceiling (/ (length str) n))))))
+      (concatenate 'string 
+                   (apply #'nconc
+                          (mapcar #'collect
+                                  (disperse! n (seq str)))))))
+
+> (defun descramble (n str)
+    (concatenate 'string
+        (collect 
+           (apply #'intersperse!
+                  (mapcar #'seq (chunk n str))))))
+
+
+> (scramble 3 "this will be scrabled, ya dig?")
+
+"tsi  rbdyd?h lbsal,ai iwlecme  g "
+
+> (descramble 3 *)
+"this will be scrambled, ya dig?  " 
+
+```
+
 ## Tutorial
 
 GTWIWTG is a tiny library for creating and using generators. 
diff --git a/examples.lisp b/examples.lisp
index df50a23..33ae013 100644
--- a/examples.lisp
+++ b/examples.lisp
@@ -122,7 +122,7 @@ vector VEC, one at a time."
 ;;; Silly Scrambler ;;; 
 
 
-(defun pad (str len &optional (pad-char #\Space]))
+(defun pad (str len &optional (pad-char #\Space))
   (let ((i 0))
     (with-output-to-string (out)
       (loop :for c :across str :do (incf i) (princ c out))