Cozenage¶

Cozenage is a Scheme-derived, Lisp-like programming language written in C, designed primarily as an educational project and exploratory implementation. It provides a small, expressive core language and is extended through a growing standard library and dynamically loadable modules.

While Cozenage borrows heavily from Scheme—particularly R5RS and R7RS—it is not intended to be fully standard-compliant. Where possible, Cozenage follows Scheme semantics and conventions, but it intentionally deviates from the standards in a number of non-trivial ways. These deviations are the result of pragmatic design choices, implementation constraints, or deliberate simplifications, and are documented where relevant.

Anyone with experience in Scheme or other Lisp dialects should find Cozenage immediately familiar.

Design goals¶

Clarity over completeness Prefer understandable, inspectable implementations over strict standards compliance.
A small, coherent core Keep the core language modest and expressive, with additional functionality layered on via libraries and modules.
Exploration and learning Cozenage exists as a vehicle for learning about language implementation, interpreter design, and runtime systems.
Practical Lisp semantics Favor straightforward, predictable behavior over obscure or highly abstract features.

Language features¶

Core object types¶

Cozenage provides the usual set of disjoint primitive objects common to Scheme-like languages:

number
string
character
symbol
pair
null
vector
boolean
port
procedure

Numeric system¶

Full numeric tower:
- integer
- rational
- real
- complex
Exact and inexact numbers
Native big integer support
Work in progress: arbitrary-precision rationals and reals

Bytevectors¶

Native bytevector types backed by C arrays:

u8, s8
u16, s16
u32, s32
u64, s64

Ports and I/O¶

File-backed text and binary ports
Memory-backed string and bytevector (u8) ports
UTF-8 Unicode support

Evaluation model¶

Proper tail-call optimization
eval / apply
Lisp-style defmacro non-hygienic macros
Delayed evaluation and streams (via the lazy library)

Runtime and tooling¶

Garbage collection (Boehm GC)
Interactive REPL with:
- multi-line editing
- persistent history
- tab completion

Polymorphic procedures¶

len
idx
rev

Intentional omissions¶

First-class continuations (``call/cc``) These are unlikely to be implemented. Control-flow patterns typically expressed using continuations may instead be provided as primitive syntax or built-in forms.
Hygienic macros While desirable, hygienic macros are complex and currently low priority. Cozenage instead provides Lisp-style, non-hygienic macros.

Features in progress¶

Arbitrary-precision rationals and reals (big integers are already supported)

Planned and future work¶

Custom line editor (replace readline/libedit)
Custom allocator / garbage collector
Expanded bytevector library
Native set and map types
Exception handling (try / catch)
Asynchronous ports (sockets)
URL-backed ports
User-defined library loading, both ‘Scheme’ libraries, and libraries written in C (ie: FFI).

Philosophy¶

Cozenage is best understood as a Scheme-inspired Lisp, prioritizing internal consistency, approachability, and educational value over exhaustive standards compliance.

Attention

This project is under active development. The documentation and the code itself changes every day. Be sure to pull from Github and build often to get the latest version.

Documentation¶

This documentation is organized into three main types. Howtos are goal-oriented documentation. They have specific goals, and demonstrate how to achieve that goal. Tutorials are knowledge-oriented documentation. They don’t have specific goals other than to introduce and demonstrate various concepts to work towards building general knowledge. The Reference is a single document which exhaustively details all the types, procedures, syntax, special forms, libraries, and even the underlying C internals of Cozenage. If you know what you are looking for, see if there is a Howto on the topic, else search for the topic in the reference. If you have no specific goal, and just want to learn more about Scheme and/or Cozenage, try a tutorial.

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