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+# zhsh
+
+An implementation of the [Zhang-Shasha]() algorithm for calculating
+tree edit distance.
+
+Here trees are s-expressions with NON-NULL leaves. 
+
+I.e. Leaves are `(and leaf (atom leaf))` 
+
+## Examples:
+
+    ZHSH> (treedist '((the cat) (sat (on (the mat)))) 
+                    '((the cat) (sat (on (the mat )))))
+    0
+    
+    ZHSH> (treedist '((the cat) (sat (on (the mat)))) 
+                    '((the cat) (sat (on (a mat )))))
+    11
+    
+    ZHSH> (treedist '((the cat) (sat (on (the mat)))) 
+                    '((the ordinary cats) (sit (on (a simple chair )))))
+    21
+    
+    ZHSH> (treedist '((the cat) (sat (on (the mat)) (for (an hour)))) 
+                    '((the ordinary cats) (sit (on (a simple chair)))))
+    26
+    
+    
+