We are trying to create a Zero

#include "axiom.as"

INT ==> Integer; 
NNI ==> NonNegativeInteger;
P ==> UnivariatePolynomial(x ,F);
FP ==> Fraction P ;
LFP ==> List FP;

NTBA(x:Symbol,F:Field): with {   
   0:% ;
   coerce: LFP -> % ;
   coerce: % -> LFP ;
   coerce: % -> OutputForm ;

   dummy:% -> % ;

}  == add {
   Rep ==> LFP;
   import from INT, NNI ;
   import from F, P, LFP ;
   import from PrintPackage ;

   0:% == per [0$FP] ;

   coerce (f:LFP):% == per f; 
   coerce (f:%):LFP == rep f;

   coerce (f:%):OutputForm == {
      a1 := rep f :: OutputForm ;
      a2 := message("D ")$OutputForm;
      hconcat(a2,a1) }

   dummy (f:%):% == {
      0$% ;
      }
}

   Compiling FriCAS source code from file 
      /var/lib/zope2.10/instance/axiom-wiki/var/LatexWiki/3380871952956020278-25px001.as
      using Aldor compiler and options 
-O -Fasy -Fao -Flsp -lfricas -Mno-ALDOR_W_WillObsolete -DFriCAS -Y $FRICAS/algebra -I $FRICAS/algebra
      Use the system command )set compiler args to change these 
      options.
   The )library system command was not called after compilation.

Let see

a := [1,2,3] :: List FRAC UP(x, FRAC INT) :: NTBA(x, FRAC INT)

   There are no library operations named NTBA 
      Use HyperDoc Browse or issue
                                )what op NTBA
      to learn if there is any operation containing " NTBA " in its 
      name.

   Cannot find a definition or applicable library operation named NTBA 
      with argument type(s) 
                                 Variable(x)
                                    Type

      Perhaps you should use "@" to indicate the required return type, 
      or "$" to specify which version of the function you need.

So there should be one ..

0$NTBA(x,FRAC INT)

   There are no library operations named NTBA 
      Use HyperDoc Browse or issue
                                )what op NTBA
      to learn if there is any operation containing " NTBA " in its 
      name.

   Cannot find a definition or applicable library operation named NTBA 
      with argument type(s) 
                                 Variable(x)
                                    Type

      Perhaps you should use "@" to indicate the required return type, 
      or "$" to specify which version of the function you need.