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 head (a)
c 
deleting new head (c)

DL macros
c b a 
deleting c
b a 
deleting a
b 
deleting b

LL macros
c b a 
deleting c
b a 
deleting a
b 
deleting b