tobthecreator / kovacs

Creating my own Lisp while rewatching Altered Carbon season 1

Kovacs

Creating my own Lisp while rewatching Altered Carbon season 1

My goal with Kovacs

The goal of this project was to get my feet wet with C again for the first time since college. When I started to learn programming when I was 10, it was with C. This is a return to my roots, getting a lot of practice with basic C project structure, pointers, and the standard C footguns (of which there are a few I didn't care to optimize my way around).

I recently learned a LISP, Scheme, and I wanted to learn about interpreters and practice C. Instead of MAL, a friend recommended this "Build Your Own Lisp", and that's the resource I'm following along with.

Build Instructions

From the main directory of this project, run

./scripts/build.sh

That should create a dist folder with the REPL's executable and the stdlib. The stdlib is read into the REPL at runtime.

Running the REPL

To run the reply, build the project, then run:

cd dist && ./kovacs.out

Installation

I'm not sure why you would want to install this little test LISP on your machine globally, but if you do, both kovacs.out and stdlib.k need to be in the same folder together. kovacs.out looks in it's folder for stdlib.k at runtime and loads the stdlib in before opening up the REPL or executing any files.

I've provided a script that moves the contents of dist into ~/bin/kovacs and adds them to your PATH via a .bashrc file. I haven't fully tested this since I am a zsh user and had to wrangle my own .zshrc to get this to work.

./scripts/install.sh

Running a .k file

You can run as many .k files as you'd like with:

./kovacs.out file1.k file2.k file3.k

These files will execute in the sequence provided.

Overview

The following overview is not finished. I need to find a version of this that matches my taste to get a better feel for the structure. I don't expect anyone to see or read this repo, but I want to leave a good paper trail for myself later.

Standard Library

You can read the full standard library in src/libs. The standard library is loaded at runtime, and also accompanies the executable for the REPL. Puruse it at your leasure.

Numbers... Well, just Integers

Instead of 1 + 2, everything is written + 1 2. Or, <operation> <arg1> ... <argn>

This is a pet project, so right now only integer numbers are supported. The behavior of those integers during division and multiplication should handle exactly like C.

Strings

We do have strings though! Strings are double quoted.

You cannot do a whole lot with strings at the moment.

You can print store them as variable: (def {x} "hello!")

You can print them as strings: print x or (print x)

Or as errors: error x or (error x)

Lists

Lists are defined by curly brackets, { }.

You can create a list with the list operation: (list 1 2 3 4).

You can get the length of a list: (len (list 1 2 3 4))

Lists are 0-indexed. To get the nth item, you can use the nth function: (nth (list 1 2 3 4))

Variables

You can declare a variable using def.

Comments

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