fix transformer for parentheses

aplr · aplr · commit fc3d0d048aa3 · 2024-03-18T13:46:32.000Z
diff --git a/lf_toolkit/parse/set/transformer.py b/lf_toolkit/parse/set/transformer.py
@@ -11,7 +11,12 @@
 
 class SymPyTransformer(SetTransformer):
     def Group(self, expr):
-        return (expr,)
+        # TODO: sympy has no concept of parentheses for sets,
+        #       so we just return the child expression for now.
+        #       If we want to check correctness of parenthesis,
+        #       we probably need to check the syntax tree we're
+        #       building, not using sympy at all.
+        return expr
 
     def Complement(self, expr):
         return Complement(UniversalSet, expr)
diff --git a/tests/parse/set/transformer_test.py b/tests/parse/set/transformer_test.py
@@ -49,7 +49,53 @@ def sympy_transformer():
             Complement(Term("A")),
             SymComplement(SymUniversalSet, SymFiniteSet(SymSymbol("A"))),
         ),
-        (Group(Term("A")), (SymFiniteSet(SymSymbol("A")),)),
+        (Group(Term("A")), SymFiniteSet(SymSymbol("A"))),
+        # ((A \ B) n (C \ (A u B)))'
+        (
+            # \overline{(A \setminus B) \cap (C \setminus (A \cup B))}
+            Complement(
+                Intersection(
+                    Difference(Term("A"), Term("B")),
+                    Difference(Term("C"), Union(Term("A"), Term("B"))),
+                )
+            ),
+            SymComplement(
+                SymUniversalSet,
+                SymIntersection(
+                    SymComplement(
+                        SymFiniteSet(SymSymbol("A")), SymFiniteSet(SymSymbol("B"))
+                    ),
+                    SymComplement(
+                        SymFiniteSet(SymSymbol("C")),
+                        SymUnion(
+                            SymFiniteSet(SymSymbol("A")), SymFiniteSet(SymSymbol("B"))
+                        ),
+                    ),
+                ),
+            ),
+        ),
+        # A' u (B' n C') u (C n B)
+        (
+            Union(
+                Complement(Term("A")),
+                Union(
+                    Group(Intersection(Complement(Term("B")), Complement(Term("C")))),
+                    Group(Intersection(Term("C"), Term("B"))),
+                ),
+            ),
+            SymUnion(
+                SymComplement(SymUniversalSet, SymFiniteSet(SymSymbol("A"))),
+                SymUnion(
+                    SymIntersection(
+                        SymComplement(SymUniversalSet, SymFiniteSet(SymSymbol("B"))),
+                        SymComplement(SymUniversalSet, SymFiniteSet(SymSymbol("C"))),
+                    ),
+                    SymIntersection(
+                        SymFiniteSet(SymSymbol("C")), SymFiniteSet(SymSymbol("B"))
+                    ),
+                ),
+            ),
+        ),
     ],
 )
 def test_sympy_transformer(
