a, b
a b
a x b
ab
a, b, c
a b c
a x b x c
abc
a, , c
a  c
a x  x c
ac
abc, def, ghi
abc def ghi
abc x def x ghi
abcdefghi
the, quick, brown, fox, jumped, over, the, lazy, dog
the quick brown fox jumped over the lazy dog
the x quick x brown x fox x jumped x over x the x lazy x dog
thequickbrownfoxjumpedoverthelazydog
this, is, a, test, to, check, the correctness,  of the, join_list , predicate

this is a test to check the correctness  of the join_list  predicate

this x is x a x test x to x check x the correctness x  of the x join_list  x predicate

thisisatesttocheckthe correctness of thejoin_list predicate

 , 	,  	 , x
  	  	  x
  x 	 x  	  x x
 	 	 x