10.5.13 `ptosfp', `sfptop'
--------------------------

ptosfp(P)
sfptop(P)
     :: $B>.I8?tM-8BBN$X$NJQ49(B, $B5UJQ49(B

RETURN
     $BB?9`<0(B

P
     $BB?9`<0(B

   * `ptosfp()' $B$O(B, $BB?9`<0$N78?t$r(B, $B8=:_@_Dj$5$l$F$$$k>.I8?tM-8BBN(B
     GF(p^N) $B$N85$KD>@\JQ49$9$k(B. $B78?t$,4{$KM-8BBN$N85$N>l9g$OJQ2=$7$J$$(B.
     $B@5@0?t$N>l9g(B, $B$^$:0L?t$G>jM>$r7W;;$7$?$"$H(B, $BI8?t(B P $B$K$h$j(B P
     $B?JE83+$7(B, P $B$r(B x $B$KCV$-49$($?B?9`<0$r(B, $B86;O85I=8=$KJQ49$9$k(B.
     $BNc$($P(B, GF(3^5) $B$O(B GF(3)[x]/(x^5+2*x+1) $B$H$7$FI=8=$5$l(B, $B$=$N3F(B
     $B85$O86;O85(B x $B$K4X$9$k$Y$-;X?t(B K $B$K$h$j(B @_K $B$H$7$F(B $BI=<($5$l$k(B.
     $B$3$N$H$-(B, $BNc$($P(B 23 = 2*3^2+3+2 $B$O(B, 2*x^2+x+2 $B$HI=8=$5$l(B,
     $B$3$l$O7k6I(B x^17 $B$HK!(B x^5+2*x+1 $B$GEy$7$$$N$G(B, @_17 $B$HJQ49$5$l$k(B.

   * `sfptop()' $B$O(B `ptosfp()' $B$N5UJQ49$G$"$k(B.

     [196] setmod_ff(3,5);
     [3,x^5+2*x+1,x]
     [197] A = ptosfp(23);
     @_17
     [198] 9*2+3+2;
     23
     [199] x^17-(2*x^2+x+2);
     x^17-2*x^2-x-2
     [200] sremm(@,x^5+2*x+1,3);
     0
     [201] sfptop(A);
     23

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

