CDL macros
c b a 
advancing head pointer
b a c 
b a c b a c b a c b 
b c a b c a b c a b 
deleting b
a c 
deleting (a)
c 
deleting (c)

DL macros
a b c 
deleting tail c
a b 
deleting head a
b 
deleting head b

LL macros
a b c 
deleting tail c
a b 
deleting head a
b 
deleting head b

