Error: Unable to deduce type for variable a in file error_deduce_type.dl at line 5
bar(a, b) :-
----^--------
Following constraints are incompatible:
   Type of variable 'a' should be a subtype of 'symbol'
   Type of variable 'a' should be a subtype of 'number' in file error_deduce_type.dl at line 6
    foo(a, b).
----^----------
1 errors generated, evaluation aborted