h.disc

来自「强大的数学工具包」· DISC 代码 · 共 41 行

                               * * * * * * *
                               *   disc    *
                               * * * * * * *

        "discriminant"
        SYNTAX: X = disc(P, x, alg)

        P is an expression whose value is a polynomial over Z or 
        Z/pZ (where p is a prime).
        x is a variable of P.
        alg is 1, 2, 3 or 4.

        X is assigned the discriminant of P with respect to the 
        variable x.
        X is computed according to the following algorithms:

        If P is a polynomial over Z:
        the algorithm of Hankel,                if alg = 1,
        the algorithm of Sylvester,             if alg = 2,
        the algorithm of Collins-Sylvester,     if alg = 3,
        the algorithm of Collins,               if alg = 4.

        If P is a polynomial over Z/pZ:
        the algorithm of Hankel,                if alg = 1,
        the algorithm of Sylvester,             if alg = 2,
        the algorithm of Collins,               if alg = 3 or 4.

        Warning: If p > 2^30, the primality of p is not tested.


        Example 1: (correct)

                disc(a*x^2 + b*x + c, x, 1)


        Example 2: (incorrect)

                disc(x*y + x^2 + 1/7 , x, 2)

_ERR_NR_041