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=[]