diff --git a/clyngor/parsing.py b/clyngor/parsing.py
index 535e747..0b36abb 100644
--- a/clyngor/parsing.py
+++ b/clyngor/parsing.py
@@ -33,8 +33,12 @@ def visit_number(self, node, children):
     def visit_args(self, node, children):
         return children
 
-    def visit_aloneargs(self, node, children):
-        return self.visit_term(node, ('', *children))
+    def visit_single_value(self, node, children):
+        return self.visit_subterm(node, children)
+    def visit_one_uplet(self, node, children):
+        return self.visit_term(node, ('', children))
+    def visit_n_uplet(self, node, children):
+        return self.visit_term(node, ('', children))
 
     def visit_text(self, node, children):
         text = tuple(children)[0] if children else ''
@@ -70,9 +74,12 @@ def ident():      return ap.RegExMatch(r'[a-z][a-zA-Z0-9_]*')
         def number():     return ap.RegExMatch(r'-?[0-9]+')
         def text():       return '"', ap.RegExMatch(r'((\\")|([^"]))*'), '"'
         def litteral():   return [text, number]
-        def subterm():    return [(ident, ap.Optional("(", args, ")")), litteral, aloneargs]
-        def args():       return subterm, ap.ZeroOrMore(',', subterm)
-        def aloneargs():  return '(', args, ')'
+        def subterm():    return [(ident, ap.Optional('(', args, ')')), litteral, aloneargs]
+        def args():       return subterm, ap.ZeroOrMore(',', subterm), ap.Optional(',')
+        def aloneargs():  return [single_value, one_uplet, n_uplet]
+        def single_value():  return '(', subterm, ')'
+        def one_uplet():  return '(', subterm, ',', ')'
+        def n_uplet():    return '(', subterm, ap.OneOrMore(',', subterm), ')'
         # NB: litteral outputed by #show are not handled.
         def term():       return ident, ap.Optional("(", args, ")")
         def terms():      return ap.ZeroOrMore(term)
diff --git a/clyngor/test/test_parsing.py b/clyngor/test/test_parsing.py
index 3cbaf30..4919e25 100644
--- a/clyngor/test/test_parsing.py
+++ b/clyngor/test/test_parsing.py
@@ -34,6 +34,13 @@ def test_parse_termset_default():
     }
     assert Parser().parse_terms(string) == expected
 
+def test_parse_tuple():
+    string = 'a(b,(2,3,(a,b)))'
+    expected = {
+        ('a', ('b', ('', (2, 3, ('', ('a', 'b')))))),
+    }
+    assert Parser().parse_terms(string) == expected
+
 def test_parse_args_without_predicat():
     string = 'a((b,10)) c("",("",""))'
     expected = {
diff --git a/clyngor/test/test_utils.py b/clyngor/test/test_utils.py
index 1ebae5a..e5d08bb 100644
--- a/clyngor/test/test_utils.py
+++ b/clyngor/test/test_utils.py
@@ -60,15 +60,16 @@ def test_answer_set_to_str():
     assert '.'.join(generate_answer_set_as_str((('a', (1, 2)), ('b', ())))) == 'a(1,2).b'
     assert ''.join(generate_answer_set_as_str((('a', (1, 2)), ('b', ())), atom_end='.')) == 'a(1,2).b.'
     assert '1'.join(generate_answer_set_as_str((('a', (1, 2)), ('b', ())), atom_end='2')) == 'a(1,2)21b2'
-    assert ' '.join(generate_answer_set_as_str((('', ('v', 2)), ('b', (['v', 3],))), atom_end='.')) == '(v,2). b((v,3)).'
+    assert ' '.join(generate_answer_set_as_str((('', ('v', 2)), ('b', (('', ['v', 3]),))), atom_end='.')) == '(v,2). b((v,3)).'
     assert ' '.join(generate_answer_set_as_str((('', ('', ('', (2,)))),))) == '("",(2,))'
+    assert '.'.join(generate_answer_set_as_str((('a', (('', ('1', '2')),)),))) == 'a((1,2))'
 
 def test_answer_set_to_str_complex():
     generate_answer_set_as_str = utils.generate_answer_set_as_str
     asp = 'a(a(2,3),(2,),b(c((d,),(e,f)))).'
-    models = tuple(ASP(asp).careful_parsing)
+    models = tuple(ASP(asp).parse_args)
     print('CAREFUL:', models)
+    answerset = models[0]
     models = tuple(ASP(asp))
     print('NORMAL :', models)
-    answerset = models[0]
     assert ' '.join(generate_answer_set_as_str(answerset, atom_end='.')) == asp
diff --git a/clyngor/utils.py b/clyngor/utils.py
index 59f9a6b..43adc67 100644
--- a/clyngor/utils.py
+++ b/clyngor/utils.py
@@ -112,7 +112,7 @@ def clingo_value_to_python(value:object) -> int or str or tuple:
                     "".format(value, type(value)))
 
 
-def python_value_to_asp(val:str or int or list or tuple, *, first_order:bool=True) -> str or tuple:
+def python_value_to_asp(val:str or int or list or tuple, *, args_of_predicate:bool=False) -> str or tuple:
     """Convert given python value in an ASP format"""
     if isinstance(val, (str, int)):
         return str(val) or '""'
@@ -122,14 +122,14 @@ def python_value_to_asp(val:str or int or list or tuple, *, first_order:bool=Tru
         assert len(val) == 2, "tuple value should be of size 2: (predicate, args))"
         predicate, args = val
         if args:
-            return predicate + python_value_to_asp(list(args), first_order=first_order)
+            return predicate + '(' + python_value_to_asp(list(args), args_of_predicate=bool(predicate)) + ')'
         else:  # no args
             return predicate
     elif isinstance(val, list):
-        ender = ',)' if len(val) == 1 and not first_order else ')'
-        return '(' + ','.join(map(python_value_to_asp.second_order, val)) + ender
+        ender = ',' if len(val) == 1 and not args_of_predicate else ''
+        return ','.join(map(python_value_to_asp, val)) + ender
     raise ValueError(f"Python value '{repr(val)}' of type {type(val)} is not convertible in ASP.")
-python_value_to_asp.second_order = lambda x: python_value_to_asp(x, first_order=False)
+# python_value_to_asp.in_predicate = lambda x: python_value_to_asp(x, args_of_predicate=True)
 
 
 def answer_set_to_str(answer_set:iter, atom_end:str='', atom_sep:str=' ') -> str: