honeylisp/kfest2021.md

Honeylisp

Introduction

• 286 project
• Honeylisp vision

Assembler

What is an assembler?

• I thought the hard part was going to be converting mnemonics to bytes
• Turns out the hard part is actually converting labels to bytes
• zero-page instructions are a different size!

How it works

• Represent each opcode as a Fennel data literal
• nest blocks arbitrarily - "lexical scope"
• multi-pass

VM

• Forth-ish stack machine
• "direct threaded" inner interpreter
• extend assembler with :vm directive
• "immediate words" are just Fennel functions

Lite

• Minimal extensible text editor built in Lua
• love2d port

Custom Editors

• imgui style
• show tile editor with map editor
• font + portrait editors based on tile editor
• generate bytes / code with fennel functions! (maps, gfx, etc)

MAME Upload

• Nod to Dagen Brock's 2016 KFest talk on GSPlus https://www.youtube.com/watch?v=1LzCmpAanpE
• Integrated Jeejah networked REPL into MAME
• Can send arbitrary Fennel code to MAME to control it
• Poke blocks of memory over the network (nREPL uses bencode from bittorrent, which allows this to be fairly low overhead)

Live Code Injection

• The assembled program is an object in memory, which we can extend interactively
• We can write new code and poke it into memory while the old code is running!
• Game code is a loop - we can have a "sync point" at the top of the loop where the state of the game is well-known
• (demo switching video modes, printing debug output, making sounds)

Hot Reload

• Because the assembled program is an object in memory

Tape generation

• Benefit of building tools in a game engine - I can just output audio
• Extended assembler to accept BASIC tokens and generate linked list of BASIC lines, so the whole thing could be bootstrapped

Disk generation

• Take a ProDOS disk image, parse it, and add files to it
• Generate loader program, rest of game can be loaded as an overlay
• New disk image is generated on every build because why not? It's fast

Neu] [ower

• Fun tricks: Random number generator (never used for gameplay purposes) = just dump a couple dozen random bytes

8-Bitsy

• Full "code-optional" environment
• Kind of awkward to actually use, but it works!
• Son drew some art
• Improvisational game design!