pointer on an operator

[evangeli@cnam.fr (Evangelista Sami)]

hello

i have declared this type :

type bin_op is (plus_op, minus_op, div_op, mod_op, ...);

i want to make a function which takes a bin_op two integers and return
the result of the operation :

function get_bin_op_result(op : bin_op; left, right : integer) return
integer is
begin
   case op is
      when plus_op  => return left + right;
      when minus_op => return left - right;
      ...
   end case;
end;

to avoid this, is there a way to make a function which return an
access to the right operator.like this :

type operator_access is access function(I1, I2 : Integer) return
Integer;
function get_operator(op : in bin_op) is
begin
   case op is
      when plus_op  => return "+"'access;
      when minus_op => return "-"'access;
      ...
   end case;
end;

then the function simply becomes :
function get_bin_op_result(op : bin_op; left, right : integer) return
integer is
begin
   return get_operator(op).all(left, right);
end;

i have tried this but the compilator complains on
"when plus_op  => return "+"'access;" :

expressions.adb:299:17: expected type "Function_Access" defined at
line 296
expressions.adb:299:17: found type access to ""+"" defined at line 29

is there a way to do this?