fix BetaNormalisingVisitor

The Visitor was missing __slots__ and a return
after visiting a reduced application

Author: Deric-W

lambda_calculus/__init__.py

@@ -4,7 +4,7 @@
 
 from .terms import Variable, Abstraction, Application
 
-__version__ = "1.6.0"
+__version__ = "1.6.1"
 __author__  = "Eric Niklas Wolf"
 __email__   = "[email protected]"
 __all__ = (

lambda_calculus/visitors/normalisation.py

@@ -19,9 +19,11 @@
 class BetaNormalisingVisitor(Visitor[Iterator[terms.Term[str]], str]):
     """
     Visitor which transforms a term into its beta normal form,
-    yielding intermediate results
+    yielding intermediate results until it is reached
     """
 
+    __slots__ = ()
+
     def visit_variable(self, variable: terms.Variable[str]) -> Iterator[terms.Variable[str]]:
         """visit a Variable term"""
         return iter(())
@@ -51,6 +53,7 @@ def visit_application(self, application: terms.Application[str]) -> Iterator[ter
                             )
                             yield reduced
                             yield from reduced.accept(self)
+                            return
                         case _:
                             abstraction = transformation
                 # no redex, continue with argument

pyproject.toml

@@ -1,6 +1,6 @@
 [project]
 name = "lambda_calculus"
-version = "1.6.0"
+version = "1.6.1"
 description = "Implementation of the Lambda calculus"
 requires-python = ">=3.10"
 keywords = []

tests/visitors/test_normalisation.py

@@ -63,14 +63,24 @@ def test_order(self) -> None:
         self.assertEqual(
             list(
                 Application(
-                    Abstraction("x", Variable("z")),
+                    Application(
+                        Abstraction("a", Variable("a")),
+                        Abstraction("x", Variable("z"))
+                    ),
                     Application(
                         triple,
                         triple
                     )
                 ).accept(self.visitor)
             ),
             [
+                Application(
+                    Abstraction("x", Variable("z")),
+                    Application(
+                        triple,
+                        triple
+                    )
+                ),
                 Variable("z")
             ]
         )