Explain the following functions:
i) makelist(i)        ii) merge(p1,p2)    iii) backpatch(p,i)

i.    makelist(i) creates a new list containing only I, an index into the array of quadruples; makelist returns a pointer to the list it has made.
ii.    merge(p1,p2) concatenates the lists pointed to by p1 and p2 , and returns a pointer to the concatenated list.
iii.    backpatch(p,i) inserts i as the target label for each of the statements on the list pointed to by p.