This domain provides a function-like type that can be queried for domain and co-domain.

#include "axiom.as"
T ==> SetCategory;

Signature(source:T, target:T): with {
  domain:%->T;
  codomain:%->T;
  coerce:(source->target)  -> %;
  coerce:%->(source->target);
  coerce:%->OutputForm;
} == (source->target) add {
  Rep == (source->target);

  domain(p:%):T == source;
  codomain(p:%):T == target;
  coerce(r:(source->target)):% == per(r);
  coerce(p:%):(source->target) == p pretend (source->target);
  coerce(p:%):OutputForm == p pretend OutputForm;
};

   Compiling FriCAS source code from file 
      /var/lib/zope2.10/instance/axiom-wiki/var/LatexWiki/sig.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.

#include "axiom.as"
T ==> SetCategory;

Signature2(source1:T, source2:T, target:T): with {
  domain:%->T;
  codomain:%->T;
  coerce:((source1,source2)->target)  -> %;
  coerce:%->((source1,source2)->target);
  coerce:%->OutputForm;
} == ((source1,source2)->target) add {
  Rep == ((source1,source2)->target);

  domain(p:%):T == Product(source1,source2);
  codomain(p:%):T == target;
  coerce(r:(source1,source2)->target):% == per(r);
  coerce(p:%):((source1,source2)->target) == p pretend ((source1,source2)->target);
  coerce(p:%):OutputForm == p pretend OutputForm;
}

   Compiling FriCAS source code from file 
      /var/lib/zope2.10/instance/axiom-wiki/var/LatexWiki/sig2.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.

f:Signature(Float, Integer)

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

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

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

f2:Signature2(Float,Float, Float)

   There are no library operations named Signature2 
      Use HyperDoc Browse or issue
                             )what op Signature2
      to learn if there is any operation containing " Signature2 " in 
      its name.

   Cannot find a definition or applicable library operation named 
      Signature2 with argument type(s) 
                                    Type
                                    Type
                                    Type

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