`prim', `cont'
--------------

prim(POLY)
     :: POLY ̌nI (primitive part).
cont(POLY)
     :: POLY ̗e (content).

RETURN POLY
     LW

   * POLY ̎ϐɊւ錴nI, eʂ߂.
   * ϐ̎w肪łȂ̂, ϐłȂϐɂČvZ
     ɂ, `ord()' ŕϐ𒲂ׂ, ̕ϐϐɂȂ悤
     ϐւČvZ, Ƃɖ߂ƂɂȂ.
   * ϐw肪ł悤ǂ̗\.

     [0] E=(y-z)*(x+y)*(x-z)*(2*x-y);
     (2*y-2*z)*x^3+(y^2-3*z*y+2*z^2)*x^2+(-y^3+z^2*y)*x+z*y^3-z^2*y^2
     [1] prim(E);
     2*x^3+(y-2*z)*x^2+(-y^2-z*y)*x+z*y^2
     [2] cont(E);
     y-z
     [3] subst(prim(subst(E,x,w,z,x),x,z,w,x);
     (y-z)*x-z*y+z^2

Q
     `var', `ord'

