New in version 2.0.
Yield all positive rationals in Cantor diagonalized order uniquely:
abjad> from abjad.tools import durationtools
abjad> generator = durationtools.yield_all_positive_rationals_in_cantor_diagonalized_order_uniquely()
abjad> for n in range(16):
... generator.next()
...
Fraction(1, 1)
Fraction(2, 1)
Fraction(1, 2)
Fraction(1, 3)
Fraction(3, 1)
Fraction(4, 1)
Fraction(3, 2)
Fraction(2, 3)
Fraction(1, 4)
Fraction(1, 5)
Fraction(5, 1)
Fraction(6, 1)
Fraction(5, 2)
Fraction(4, 3)
Fraction(3, 4)
Fraction(2, 5)
Return fraction generator.