LIB "tst.lib"; tst_init();
  gcd(2,3);
  gcd(bigint(2)^20,bigint(3)^23);     // also applicable for bigints
  typeof(_);
  ring r=0,(x,y,z),lp;
  gcd(3x2*(x+y),9x*(y2-x2));
  ring rr=integer,x,dp;
  gcd(number(6472674604870),number(878646537247372));
tst_status(1);$