lambda-ast-explorer.org

Lambda Calculus AST Explorer

Lambda Calculus AST Explorer

This tool explores the Abstract Syntax Trees (ASTs) of lambda calculus expressions in Python, focusing on pair, first, and rest functions with list representations.

Implementation

# full lambda_ast_explorer.py code here

Example: List Construction and Manipulation

Let’s explore how the AST represents a simple list expression like ‘(1 2 3 ‘(4 5))

from lambda_ast_explorer import make_list, first, rest, print_list

# Create the list structure: (1 2 3 (4 5))
nested_list = make_list(1, 2, 3, make_list(4, 5))

# Print the list
print("List representation:")
print(print_list(nested_list))

# Access elements
print("\nAccessing elements:")
print(f"First element: {first(nested_list)}")
print(f"Rest of list: {print_list(rest(nested_list))}")
print(f"Third element: {first(rest(rest(nested_list)))}")
print(f"Nested list: {print_list(first(rest(rest(rest(nested_list)))))}")

Mermaid Diagram: Lambda Calculus List Structure

flowchart TD
    A["pair(1, ...)"] -->|first| B[1]
    A -->|rest| C["pair(2, ...)"]
    C -->|first| D[2]
    C -->|rest| E["pair(3, ...)"]
    E -->|first| F[3]
    E -->|rest| G["pair((4 5), ...)"]
    G -->|first| H["pair(4, ...)"]
    G -->|rest| I[None]
    H -->|first| J[4]
    H -->|rest| K["pair(5, ...)"]
    K -->|first| L[5]
    K -->|rest| M[None]

Loading

Exploring AST Transformations

Next, examine how Python’s AST represents these lambda expressions.

import ast
import astunparse

# Define a simple lambda expression
expr = "lambda x: lambda y: x(y)"

# Parse and print the AST
tree = ast.parse(expr)
print(ast.dump(tree, indent=2))

# Modify the AST 
# (example: transform to a composed function)
transformed = ast.parse("lambda x, y: x(y)")
print("\nTransformed AST:")
print(ast.dump(transformed, indent=2))

# Convert back to source code
print("\nOriginal source:")
print(astunparse.unparse(tree))
print("\nTransformed source:")
print(astunparse.unparse(transformed))