`characteristic_ff'
-------------------

characteristic_ff()
     :: $B@_Dj$5$l$F$$$kBN$NI8?t(B

RETURN
     $B@0?t(B

   * $B@_Dj$5$l$F$$$kBN$NI8?t$rJV$9(B.

   * GF(p) $B$N>l9g(B p, GF(2^n) $B$N>l9g(B 2 $B$rJV$9(B.

     [0] characteristic_ff();
     characteristic_ff : current_ff is not set
     return to toplevel
     [0] setmod_ff(3);
     3
     [1] characteristic_ff();
     3
     [2] setmod_ff(x^2+x+1);
     x^2+x+1
     [3] characteristic_ff();
     2

$B;2>H(B
     *Note `setmod_ff': setmod_ff

