PyLisp

A Lisp interpreter written in Python loosely following John McCarthy's Recursive Functions of Symbolic Expressions and Their Computation by Machine and Common Lisp implementation.

Functions Implemented:

• CAR: Get the head of a construct
• CDR: Get the tail of a construct
• CONS: Construct memory object holding two values
• ATOM: Check if an expression is atomic
• EQ: check if two expressions are equal atomically
• LIST: Create a chain construct that resembles a list
• QUOTE: Return rest of expression
• ASSOC: Associate the values of two lists as pairs
• Prefix Arithmatic: +, -, *, /
• APPEND: Append to a list a value
• PRINT: Print a value
• LET: Bind variables inside a scope and execute expression
• DEFUN: Define a function
• SET: Set a variable
• IF: If statement
• PROGN: Do more than one statement

What is not implemented:

• Error management
• Defmacro implementation
• Package management
• File Handling I am planning to redo this project in the future, but as for now, this implementation does not have the previous mentioned features.

Usage

• To use this implementation of lisp, simply run the python script where a prompt PyLisp> will be waiting for input.
• To load in a lisp file, simply write PyLisp> load <file-dir> when you're in the prompt.
• You can use test.lisp file as an example where loading it would be as follows

PyLisp> load test.lisp
1
2
3
4
------------------------
(1 . 2)
(3 . 4)
(4 . 5)
T

Purpose of the Project:

The idea for this project is to implement the notions learned in CPS 710 Compilers and Interpreters at (Previously called) Ryerson University. Furthermore, it is to implement a LISP interpreter following John McCarthy's original paper, and see what his logic was in each predicate he made.