compare
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.
Return
a negative number if @a comes before @b, 0 if they are equal, and a positive number if @a comes after @b
Since
2.14
Parameters
b
a #GSequenceIter