from .math_rational_rational import rational_from_wide, rational_parts
from .math_rational_types import Rational


def subtract_rational(a: Rational, b: Rational) -> Rational:
    """a - b, reduced."""
    an, ad = rational_parts(a)
    bn, bd = rational_parts(b)
    return rational_from_wide(an * bd - bn * ad, ad * bd)