add BetaNormalisingVisitor.skip_intermediate

Author: Deric-W

lambda_calculus/__init__.py

@@ -4,7 +4,7 @@
 
 from .terms import Variable, Abstraction, Application
 
-__version__ = "1.6.1"
+__version__ = "1.7.0"
 __author__  = "Eric Niklas Wolf"
 __email__   = "[email protected]"
 __all__ = (

lambda_calculus/visitors/normalisation.py

@@ -24,6 +24,13 @@ class BetaNormalisingVisitor(Visitor[Iterator[terms.Term[str]], str]):
 
     __slots__ = ()
 
+    def skip_intermediate(self, term: terms.Term[str]) -> terms.Term[str]:
+        """return the beta normal form directly"""
+        result = term
+        for intermediate in term.accept(self):
+            result = intermediate
+        return result
+
     def visit_variable(self, variable: terms.Variable[str]) -> Iterator[terms.Variable[str]]:
         """visit a Variable term"""
         return iter(())

pyproject.toml

@@ -1,6 +1,6 @@
 [project]
 name = "lambda_calculus"
-version = "1.6.1"
+version = "1.7.0"
 description = "Implementation of the Lambda calculus"
 requires-python = ">=3.10"
 keywords = []

tests/visitors/test_normalisation.py

@@ -119,3 +119,16 @@ def test_no_normal_form(self) -> None:
             if iteration > 10:
                 break
             self.assertEqual(transformation, term)
+
+    def test_skip_intermediate(self) -> None:
+        """test skipping of intermediate results"""
+        self.assertEqual(
+            self.visitor.skip_intermediate(Abstraction("a", Variable("z"))),
+            Abstraction("a", Variable("z"))
+        )
+        self.assertEqual(
+            self.visitor.skip_intermediate(
+                Application(Abstraction("a", Variable("a")), Variable("z"))
+            ),
+            Variable("z")
+        )