add logic lambda terms

Author: Deric-W

lambda_calculus/__init__.py

@@ -4,7 +4,7 @@
 
 from .terms import Variable, Abstraction, Application
 
-__version__ = "1.8.0"
+__version__ = "1.9.0"
 __author__  = "Eric Niklas Wolf"
 __email__   = "[email protected]"
 __all__ = (

lambda_calculus/terms/__init__.py

@@ -16,7 +16,8 @@
     "Variable",
     "Abstraction",
     "Application",
-    "arithmetic"
+    "arithmetic",
+    "logic"
 )
 
 T = TypeVar("T")

lambda_calculus/terms/logic.py

@@ -0,0 +1,32 @@
+#!/usr/bin/python3
+
+"""Implementations of boolean values and logical operators"""
+
+from . import Variable, Abstraction, Application
+
+__all__ = (
+    "TRUE",
+    "FALSE",
+    "AND",
+    "OR",
+    "NOT",
+    "IF_THEN_ELSE"
+)
+
+TRUE = Abstraction.curried(("x", "y"), Variable("x"))
+FALSE = Abstraction.curried(("x", "y"), Variable("y"))
+
+AND = Abstraction.curried(
+    ("p", "q"),
+    Application.with_arguments(Variable("p"), (Variable("q"), Variable("p")))
+)
+OR = Abstraction.curried(
+    ("p", "q"),
+    Application.with_arguments(Variable("p"), (Variable("p"), Variable("q")))
+)
+NOT = Abstraction("p", Application.with_arguments(Variable("p"), (FALSE, TRUE)))
+
+IF_THEN_ELSE = Abstraction.curried(
+    ("p", "a", "b"),
+    Application.with_arguments(Variable("p"), (Variable("a"), Variable("b")))
+)

pyproject.toml

@@ -1,6 +1,6 @@
 [project]
 name = "lambda_calculus"
-version = "1.8.0"
+version = "1.9.0"
 description = "Implementation of the Lambda calculus"
 requires-python = ">=3.10"
 keywords = []

tests/terms/test_logic.py

@@ -0,0 +1,80 @@
+#!/usr/bin/python3
+
+"""Tests for logic terms"""
+
+from unittest import TestCase
+from collections.abc import Iterable, Iterator
+from lambda_calculus.visitors.normalisation import BetaNormalisingVisitor
+from lambda_calculus.terms import Term, Variable, Application, logic
+
+
+class LogicTest(TestCase):
+    """Test for logic terms"""
+
+    visitor: BetaNormalisingVisitor
+
+    def setUp(self) -> None:
+        """create a visitor"""
+        self.visitor = BetaNormalisingVisitor()
+
+    def make_truth_table(self, outputs: Iterable[Term[str]]) -> Iterator[tuple[tuple[Term[str], Term[str]], Term[str]]]:
+        """make a truth table with two inputs"""
+        inputs = (
+            (logic.FALSE, logic.FALSE),
+            (logic.TRUE, logic.FALSE),
+            (logic.FALSE, logic.TRUE),
+            (logic.TRUE, logic.TRUE)
+        )
+        return zip(inputs, outputs)
+
+    def test_and(self) -> None:
+        """test logical and"""
+        for (a, b), c in self.make_truth_table((logic.FALSE,) * 3 + (logic.TRUE,)):
+            self.assertEqual(
+                self.visitor.skip_intermediate(
+                    Application.with_arguments(logic.AND, (a, b))
+                ),
+                c
+            )
+
+    def test_or(self) -> None:
+        """test logical or"""
+        for (a, b), c in self.make_truth_table((logic.FALSE,) + (logic.TRUE,) * 3):
+            self.assertEqual(
+                self.visitor.skip_intermediate(
+                    Application.with_arguments(logic.OR, (a, b))
+                ),
+                c
+            )
+
+    def test_not(self) -> None:
+        """test logical negation"""
+        self.assertEqual(
+            self.visitor.skip_intermediate(Application(logic.NOT, logic.TRUE)),
+            logic.FALSE
+        )
+        self.assertEqual(
+            self.visitor.skip_intermediate(Application(logic.NOT, logic.FALSE)),
+            logic.TRUE
+        )
+
+    def test_if_then_else(self) -> None:
+        """test if statement"""
+        self.assertEqual(
+            self.visitor.skip_intermediate(
+                Application.with_arguments(
+                    logic.IF_THEN_ELSE,
+                    (logic.TRUE, Variable("a"), Variable("b"))
+                )
+            ),
+            Variable("a")
+        )
+        self.assertEqual(
+            self.visitor.skip_intermediate(
+                Application.with_arguments(
+                    logic.IF_THEN_ELSE,
+                    (logic.FALSE, Variable("a"), Variable("b"))
+                )
+            ),
+            Variable("b")
+        )