6.3.13 `ediff'
--------------

ediff(POLY[,VARN]*)

ediff(POLY,VARLIST)
     :: POLY $B$r(B VARN $B$"$k$$$O(B VARLIST $B$NCf$NJQ?t$G=g<!%*%$%i!<HyJ,$9$k(B.

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

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

VARN
     $BITDj85(B

VARLIST
     $BITDj85$N%j%9%H(B

   * $B:8B&$NITDj85$h$j(B, $B=g$K%*%$%i!<HyJ,$7$F$$$/(B. $B$D$^$j(B,
     ediff(POLY,x,y) $B$O(B, ediff(ediff(POLY,x),y) $B$HF1$8$G$"$k(B.

     [0] ediff((x+2*y)^2,x);
     2*x^2+4*y*x
     [1] ediff((x+2*y)^2,x,y);
     4*y*x

