`gcd', `gcdz'
-------------

gcd(POLY1,POLY2)
gcdz(POLY1,POLY2)
     :: POLY1  POLY2  gcd.

RETURN
     ¿༰
POLY1,POLY2
     ¿༰

   * Ĥ¿༰κ (GCD) . `gcd()' , ͭξ
     ¿༰ȤƤ GCD ֤. ʤ, ̤, ķ 
     GCD 1 ˤʤ褦¿༰, ޤ, ߤǤξ 1 ֤. 
     `gcdz()', POLY1, POLY2 Ȥξ, ľ¿༰
     ȤƤ GCD ֤. ʤ, `gcd()' ͤ, Τ GCD
     ͤݤΤ֤.
   * Extended Zassenhaus 르ꥺ (EZGCD) ˤ.

     [0] gcd(12*(x^2+2*x+1)^2,18*(x^2+(y+1)*x+y)^3);
     x^3+3*x^2+3*x+1
     [0] gcdz(12*(x^2+2*x+1)^2,18*(x^2+(y+1)*x+y)^3);
     6*x^3+18*x^2+18*x+6


     `igcd'

