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

prim(POLY)
     :: POLY θŪʬ (primitive part).
cont(POLY)
     :: POLY  (content).

RETURN POLY
     ͭ¿༰

   * POLY μѿ˴ؤ븶Ūʬ, ̤.
   * ѿλ꤬ǤʤΤ, ѿǤʤѿˤĤƷ׻
     ˤ, `ord()' ѿĴ٤, ѿѿˤʤ褦
     ѿؤƷ׻, Ȥ᤹Ȥˤʤ.
   * ѿ꤬Ǥ褦ɤͽ.

     [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


     `var', `ord'

