Change theory function name field to string field.

Clingo allows theory function names to be symbols like + and - (in
fact, that is how parsed theory terms are represented, e.g. the
unparsed theory term "a + b" is parsed into a theory function with
name + and arguments a, b. Therefore, restricting the name field to be
a constant field (as it was before this change) would be incorrect.

src/renopro/predicates.py

@@ -524,7 +524,7 @@ class TheoryFunction(AstPredicate):
     """
 
     id = IdentifierField
-    name = ConstantField
+    name = StringField
     arguments = TheoryTerms.unary.Field
 
 

tests/asp/reify_reflect/reified/theory_function.lp

@@ -5,6 +5,6 @@ theory_atom(4,function(5),theory_atom_elements(7),theory_guard(13)).
 function(5,a,terms(6)).
 theory_atom_elements(7,0,theory_terms(8),literals(12)).
 theory_terms(8,0,theory_function(9)).
-theory_function(9,f,theory_terms(10)).
+theory_function(9,"f",theory_terms(10)).
 theory_terms(10,0,number(11)).
 number(11,1).