Blend65

⚠️ DEVELOPMENT STATUS: 60-70% COMPLETE

The compiler frontend is fully functional with production-quality lexer, parser, and semantic analyzer. The backend (IL generation and 6502 code generation) is in development. While the compiler can parse and validate Blend65 programs, it cannot yet generate executable code for the Commodore 64.

Current milestone: 2,428 tests passing | Next phase: IL Generator

Overview

Blend65 is a modern programming language compiler targeting 6502-based systems including the Commodore 64, VIC-20, and Commander X16. The language provides modern programming constructs while generating efficient assembly code for vintage hardware.

Language Features

The language syntax combines familiar programming concepts with direct hardware access:

module C64Game.Snake

import setSpritePosition, enableSprite from c64.sprites
import joystickLeft, joystickRight from c64.input
import playNote from c64.sid

@zp var snakeX: byte = 160     // Zero-page variable allocation
var score: word = 0            // 16-bit integer
var gameState: GameState = PLAYING

enum GameState
    MENU, PLAYING, GAME_OVER
end enum

function updateSnake(): void
    if joystickLeft() then
        snakeX = snakeX - 2
    end if

    setSpritePosition(0, snakeX, 100)

    if snakeX == appleX then
        score = score + 10
        playNote(0, 440)
    end if
end function

Storage Classes

Variables can be declared with specific memory allocation strategies:

• @zp var - Zero page allocation for fastest access
• @ram var - Standard RAM allocation
• @data var - Initialized data section
• var - Same as @ram var

Memory-Mapped Hardware

The @map system provides type-safe access to hardware registers (unique to Blend65):

// Simple register mapping
@map borderColor at $D020: byte

// Structured layout mapping
@map vic at $D000 layout
    spriteX: at $00: byte[8]
    borderColor: at $20: byte
    backgroundColor: at $21: byte
end @map

// Type-based mapping
@map sid at $D400 type SIDRegisters

// Usage - clean, self-documenting hardware access
vic.borderColor = LIGHT_BLUE
sid.voice1.frequency = 440

Callback Functions

Type-safe function pointers enable interrupt-driven programming and behavioral dispatch:

callback interruptHandler: function(): void
callback behaviorFunction: function(entity: Entity): void

var rasterCallbacks: interruptHandler[8]
var enemyBehaviors: behaviorFunction[16]

Target Platforms

• Commodore 64 - Full VIC-II, SID, and CIA support
• VIC-20 - VIA and basic graphics support
• Commander X16 - VERA graphics and enhanced features
• Generic 6502 - Basic instruction set compatibility

Implementation Status

Compiler Pipeline:

Source → Lexer ✅ → Parser ✅ → AST ✅ → Semantic ✅ → IL 🔜 → CodeGen 🔜 → Assembly 🔜

Completed (60-70%)

Component	Tests	Status
Lexer	150+	✅ Production-ready
Parser	400+	✅ Production-ready
AST System	100+	✅ Production-ready
Semantic Analyzer	1,365+	✅ Production-ready
Advanced Analysis (Phase 8)	500+	✅ Complete
Hardware Analyzers (C64/C128/X16)	200+	✅ Complete
Integration Tests	313+	✅ Passing

Semantic Analysis Highlights:

• Complete type checking with multi-module support
• Control flow analysis with CFG construction
• Definite assignment and variable usage tracking
• Dead code and unused function detection
• Data flow analysis (reaching definitions, liveness, constant propagation)
• Escape analysis and purity analysis for optimization hints
• C64-specific hardware analysis (VIC-II timing, SID conflict detection)

In Development

• IL Generator - Intermediate language for optimization and portability
• Code Generator - 6502 instruction selection and register allocation
• Assembler Integration - PRG file generation

Planned

• Standard library (VIC-II, SID, CIA wrappers)
• Additional examples and documentation
• Performance optimization passes

Development

This project uses TypeScript and is organized as a monorepo with Yarn workspaces.

# Install dependencies
yarn install

# Build all packages
yarn build

# Run tests
yarn test

# Clean build artifacts
yarn clean

# Build, clean, and test (full validation)
yarn clean && yarn build && yarn test

Requirements:

• Node.js >= 22.0.0
• Yarn 1.x (< 2.0.0)

Project Structure

blend65/
├── packages/
│   └── compiler/          # Main compiler package
│       └── src/
│           ├── lexer/     # Tokenization
│           ├── parser/    # Syntax parsing
│           ├── ast/       # AST nodes and utilities
│           ├── semantic/  # Type checking and analysis
│           └── target/    # Code generation (WIP)
├── docs/
│   └── language-specification/  # Complete language spec
├── examples/              # Example Blend65 programs
└── plans/                 # Development roadmap

Documentation

• Language Specification - Complete syntax and semantics reference
• Compiler Master Plan - Implementation roadmap and status

License

📜 Elastic License 2.0 (ELv2)

This software is licensed under the Elastic License 2.0. You are free to use it to create games and software, but you cannot sell the compiler itself or offer it as a service. See LICENSE for full details.

Use Case	Allowed
Create open-source games/software	✅ Yes
Create commercial games/software	✅ Yes
Modify Blend65 for your own use	✅ Yes
Contribute improvements back	✅ Yes
Sell Blend65 as a product	❌ No
Include Blend65 in a commercial tool	❌ No
Offer Blend65 as a hosted service	❌ No
Fork to create competing compiler	❌ No

Contributing

The project is under active development. See the master plan for current priorities and the implementation roadmap.