Epsilon is a Lisp programming environment built on top of SBCL that provides functional data structures, data encoding, cryptographic functionality, and network programming capabilities.

It is a new project and is evolving. Feedback is welcome!

• Structures - Immutable maps, sets, and sequences with structural sharing
• Encoding - JSON, YAML, MessagePack, Base64, and binary format support
• Cryptography - SHA-2 family hashing, CRC-32, and Adler-32 checksums
• Networking - HTTP client/server with TLS support
• Tools - Build system, test framework, and benchmarking utilities
• No Dependencies - Depends only upon SBCL built-in modules

Install Epsilon runtime:

curl -sSL https://raw.githubusercontent.com/jbouwman/epsilon/main/scripts/install.sh | bash

This installs a complete runtime.

Download the appropriate release for your platform from GitHub Releases:

• epsilon-macos-arm64.tar.gz - macOS Apple Silicon
• epsilon-linux-x86_64.tar.gz - Linux x86_64

# Interactive REPL
./epsilon

# Evaluate expressions  
./epsilon --eval "(format t \"Hello, World\")"

# Load specific module
./epsilon --module epsilon.json --eval "(json:encode '(:foo \"bar\"))"

# List available modules
./epsilon --modules

# Test specific module
./epsilon --test epsilon.core

# Test specific package within a module
./epsilon --test epsilon.core:epsilon.log.tests

# Test specific test by name
./epsilon --test epsilon.core:epsilon.log.tests:test-detailed-formatter

# Test with verbose output for debugging
./epsilon --test epsilon.core --verbose
./epsilon --test epsilon.core:epsilon.log.tests:test-detailed-formatter --verbose

# Self-test all modules
./epsilon --exec epsilon.release:selftest

# Run all tests with JUnit output
./epsilon --exec epsilon.release:selftest --format junit --file target/TEST-results.xml

# Run CLI smoke tests
./scripts/smoke.sh

For development setup and contributing:

# Clone repository
git clone https://github.com/jbouwman/epsilon.git
cd epsilon

# Run tests
./scripts/test.sh

# Build documentation
./scripts/build.sh

# Create a release (maintainers)
./scripts/release.sh --dry-run 0.11.0

See RELEASE.md for complete release documentation.

Epsilon is a Lisp programming environment built on SBCL with a modular architecture. The codebase follows functional programming principles with immutable data structures and protocol-based extensibility.

Each module in /modules/ contains a module.lisp file defining dependencies and exports. Modules are loaded via epsilon.loader which handles dependency resolution and incremental compilation. Core bootstrap happens through /modules/core/src/boot.lisp.

• Functional Data Structures: Maps, sets, and sequences with structural sharing (modules/core/src/lib/)
• Protocol-based Design: Extension points via epsilon.protocol for polymorphic behavior
• Platform Abstraction: Platform-specific modules (darwin/linux/windows) handle OS differences
• Resource Management: Connection pooling in HTTP client, proper cleanup in all I/O operations
• Transducers: Composable algorithmic transformations in modules/core/src/lib/transducer.lisp

The custom test framework (epsilon.test) supports hierarchical test organization with fixtures. Tests use deftest macro and assertions like is, is-=, is-equal. Tests can output to shell, REPL, or JUnit XML format.

Core modules form a dependency hierarchy:

• epsilon.core: Foundation (no dependencies)
• epsilon.test: Testing framework (depends on core)
• epsilon.http: HTTP client/server (depends on core, tls)
• epsilon.json/yaml/msgpack: Data formats (depend on core)
• epsilon.lsp: Language Server Protocol (depends on json, http)

• Lisp naming conventions: lowercase with hyphens
• Packages export symbols explicitly via defpackage
• Functional style preferred: avoid mutation, use pure functions
• Proper docstrings for public APIs
• Indentation follows standard Lisp conventions

Documentation