Method __sub__

algorithms/math/polynomial.py:435–482

Subtract a polynomial, monomial, or scalar from this polynomial. Args: other: Value to subtract. Returns: The resulting Polynomial. Raises: ValueError: If other is not a valid type.

(self, other: int | float | Fraction | Monomial)

            )

    def __sub__(self, other: int | float | Fraction | Monomial) -> Polynomial:
        """Subtract a polynomial, monomial, or scalar from this polynomial.

        Args:
            other: Value to subtract.

        Returns:
            The resulting Polynomial.

        Raises:
            ValueError: If other is not a valid type.
        """
        if isinstance(other, (int, float, Fraction)):
            return self.__sub__(
                Monomial({}, Polynomial._rationalize_if_possible(other))
            )
        elif isinstance(other, Monomial):
            monos = {m.clone() for m in self.all_monomials()}
            for _own_monos in monos:
                if _own_monos.equal_upto_scalar(other):
                    scalar = _own_monos.coeff
                    monos -= {_own_monos}
                    temp_variables = {i: other.variables[i] for i in other.variables}
                    monos |= {
                        Monomial(
                            temp_variables,
                            Polynomial._rationalize_if_possible(scalar - other.coeff),
                        )
                    }
                    return Polynomial([z for z in monos])

            to_insert = other.clone()
            to_insert.coeff *= -1

            monos |= {to_insert}
            return Polynomial([z for z in monos])

        elif isinstance(other, Polynomial):
            p = Polynomial(list(z for z in {m.clone() for m in self.all_monomials()}))
            for o in other.all_monomials():
                p = p.__sub__(o.clone())
            return p

        else:
            raise ValueError(
                "Can only subtract int, float, Fraction, "
                "Monomials, or Polynomials from Polynomials."
            )

    def __mul__(self, other: int | float | Fraction | Monomial) -> Polynomial:
        """Multiply this polynomial by another polynomial, monomial, or scalar.