h.ecnpscf

来自「强大的数学工具包」· ECNPSCF 代码 · 共 44 行

                         * * * * * * *
                         *  ecnpscf  *
                         * * * * * * *

        "elliptic curve with point order with small cofactor"
        SYNTAX: X = ecnpscf(p,cf)
                X = ecnpscf(cf)

        p is an expression whose value is a prime > 3. cf is an 
        integer.

        In the first case, ecnpscf determines an elliptic curve
        in short Weierstrass normal form over Q, which has a point
        order with cofactor <= cf over Z/pZ.
        In the second case, ecnpscf determines an elliptic curve
        in short Weierstrass normal form over the current Modulus,
        which has a point order with cofactor <= cf. 
        X is assigned this elliptic curve.

        The number of points of the curve X modulo p is stored 
        in AV (see "?avfunc")


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


        Example 1: (correct)

                ecnpscf(10000000000000000000001993,100)


        Example 2: (correct)

                ecnpscf(99);


        Example 3: (incorrect)

                ecnpscf(100,3);

_ERR_NR_328