SequenceIterCompareFunc

A SequenceIterCompareFunc is a function used to compare iterators.

It must return zero if the iterators compare equal, a negative value if a comes before b, and a positive value if b comes before a.

Parameters:

a	a SequenceIter
b	a SequenceIter
data	user data

Returns:

zero if the iterators are equal, a negative value if a comes before b, and a positive value if b comes before a.