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 matters2.

[X]=[b,a,d]fails ---the two lists are of different lengths3.

[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 listcan't be deconstructed

6.

[XY]=[[a,[b,c]],d]succeeds with

X=[a,[b,c]],Y=[d]7.

[XY]=[a]succeeds withX=a,Y=[]

Mon May 24 20:14:48 BST 1999