Some Possible Matches

We now illustrate how two lists unify and in what circumstances two lists fail to unify.

1. 		  [b
a
d]=[d
a
b] 		     fails ---as the order matters



2. 		  [X]=[b
a
d]     		     fails ---the two lists are of different lengths



3. 		  [XY]=[he
is
a
cat]		 succeeds with



 X=he
 Y=[is
a
cat]



4. 		  [X
YZ]=[a
b
c
d] 		  succeeds with



 X=a
 Y=b
 Z=[c
d]



5. 		  [XY]=[]	       		 fails ---the empty list



can't be deconstructed



6. 		  [XY]=[[a
[b
c]]
d] 		succeeds with



 X=[a
[b
c]]
 Y=[d]



7. 		  [XY]=[a] 		 succeeds with  X=a
 Y=[]