Returns a negative number if a comes before b, 0 if they are equal,
and a positive number if a comes after b.
The a and b iterators must point into the same sequence.
a #GSequenceIter
Returns the position of iter
Returns the #GSequence that iter points into.
Returns whether iter is the begin iterator
Returns whether iter is the end iterator
Returns the #GSequenceIter which is delta positions away from iter.
If iter is closer than -delta positions to the beginning of the sequence,
the begin iterator is returned. If iter is closer than delta positions
to the end of the sequence, the end iterator is returned.
A positive or negative number indicating how many positions away from iter the returned #GSequenceIter will be
Returns an iterator pointing to the next position after iter.
If iter is the end iterator, the end iterator is returned.
Returns an iterator pointing to the previous position before iter.
If iter is the begin iterator, the begin iterator is returned.
The #GSequenceIter struct is an opaque data type representing an iterator pointing into a #GSequence.