Fix example correctness

Author: anubh-v

src/examples/liars.js

@@ -1,17 +1,26 @@
+function distinct(items) {                                                  
+     return is_null(items)                                                     
+         ? true                                                                
+         : is_null(tail(items))                                                
+         ? true                                                                
+         : is_null(member(head(items), tail(items)))                           
+             ? distinct(tail(items))                                           
+             : false;                                                          
+}
 
 const betty = amb(1, 2, 3, 4, 5);
 const ethel = amb(1, 2, 3, 4, 5);
 const joan = amb(1, 2, 3, 4, 5);
 const kitty = amb(1, 2, 3, 4, 5);
 const mary = amb(1, 2, 3, 4, 5);
 
-require((kitty === 2) || (betty === 3));
-require((ethel === 1) || (joan === 2));
-require((joan === 3) || (ethel === 5));
-require((kitty === 2) || (mary === 4));
-require((mary === 4) || (betty === 1));
+require(amb(kitty === 2, betty === 3));
+require(amb(ethel === 1, joan === 2));
+require(amb(joan === 3, ethel === 5));
+require(amb(kitty === 2, mary === 4));
+require(amb(mary === 4, betty === 1));
 
 require(distinct(list(betty, ethel, joan, kitty, mary)));
 
 list(list('betty', betty), list('ethel', ethel), list('joan', joan),
-     list('kitty', kitty), list('mary', mary));
+  list('kitty', kitty), list('mary', mary));