Awesome Common Lisp

A curated list of awesome Common Lisp libraries.

For awesome software, see lisp-lang.org’s success stories and the awesome-cl-software list.

All libraries listed here are available from Quicklisp unless stated otherwise. The ones marked with a ⭐ are so widespread and solid that they became community standards. You can’t be wrong with them. This is the case for Quicklisp, BordeauxThreads and such. Libraries denoted with a 👍 are the ones we like and want to promote here at the Awesome-cl list. They proved solid, they may solve a problem better than a community standard but they aren’t as widespread, or not considered as stable. For example, we prefer Spinneret over Cl-Who.

Add something new! See the contributing section for adding something to the list.

This is released under the GNU Free Documentation License - its text is provided in the LICENSE file. This repository is also mirrored on NotABug - a fully-free (as in libre) alternative to Github. Preference is given to free software and sellers who aren’t evil for physical resources.

Table of Contents

• Audio
• Build Systems
• Compilers, code generators
  • APL
  • C, C++
• Crypto
• Cryptocurrencies
• Database
  • ORMs
  • Persistent object databases
  • Graph databases
  • Wrappers
  • Migration tools
  • To third parties
  • Tools
• Data Structures
• Docker images
• Foreign Function Interface, languages interop
  • C
  • Clojure
  • Erlang
  • Java
  • Objective-C
  • Python
  • .Net Core
  • Miscellaneous
• Game Development
• Graphics
• GUI
  • Mobile
• Implementations
• JSON
• YAML
• Language extensions
  • Portability layers
  • Changing the syntax
  • CLOS extensions
  • Function extensions
  • Iteration
  • Lambda shorthands
  • Non-deterministic, logic programming
  • Reactive programming
  • Contract programming
  • Typing
• Learning and Tutorials
  • Online
  • Beginner
  • Intermediate
  • Advanced
  • Web Development
  • Reference
  • Offline
  • Beginner
  • Intermediate
  • Advanced
  • Other books
  • Community
• Library Manager
  • Interfaces to other package managers
• Machine Learning
• Natural Language Processing
• Network and Internet
  • HTTP clients
  • HTTP Servers
    • Hunchentoot plugins
    • Clack plugins
  • Web frameworks
  • Isomorphic web frameworks
  • Assets management
  • Parsing html
  • Querying HTML/DOM
  • HTML generators and templates
  • URI handling
  • Javascript
  • Email
  • Websockets
  • Static site generators
  • Deployment
  • Monitoring
  • Third-party APIs
  • Web project skeletons and generators
  • Others
• Numerical and Scientific
  • Matrix libraries
  • Statistics
  • Units
  • Utils
• Parallelism and Concurrency
  • Actors pattern
  • Event processing
  • Job processing
• Regex
• Scripting
  • Writing, running scripts
  • Command-line options parsers
  • Readline, ncurses and other graphical helpers
  • Shells, shells interfaces
  • System administration
  • Other scripting utilities
• Text Editor Resources
  • Emacs
  • Vim & Neovim
  • Eclipse
  • Lem
  • Atom
  • Sublime Text
  • VSCode
  • Geany (experimental)
  • Notebooks
  • REPLs
  • Online editors
  • Apps
• Text Parsers
• Text Processing
• Tools
• Unit Testing
• Utilities
  • Caching
  • Compression / decompression
  • Configuration
  • CSV
  • Date and time
  • Data validation
  • Developer utilities
  • Documentation builders
  • Files and directories
  • Git
  • i18n
  • Linting, code formatting
  • Literate programming
  • Logging
  • Markdown
  • PDF
  • Plotting
  • Project skeletons
  • Security
  • XML
  • Other
• Contributing

Audio

• Open Music - a visual programming, computer-aided composition environment. GPL3.
• OM7 - a new implementation of the OpenMusic visual programming and computer-aided composition environment including a number of improvements on graphical interface, computational mode, and connection to external software libraries. GPL3.
• Incudine - Music/DSP programming environment for Common Lisp. Useful to design software synthesizers or sound plugins from scratch. It is also a compositional tool that allows to produce high quality sounds controllable at the sample level, defining and redefining the digital signal processors and the musical structures on-the-fly.
• cl-collider - A SuperCollider client for CommonLisp. With a tutorial and live coding demos. Public domain.
• csound - A sound and music computing system. Includes CFFI and FFI interfaces for Common Lisp.
• CLM - Common Lisp Music is a music synthesis and signal processing package in the Music V family. It provides much the same functionality as Stk, Csound, SuperCollider, PD, CMix, cmusic, and Arctic — a collection of functions that create and manipulate sounds, aimed primarily at composers (in CLM’s case anyway).
• cl-patterns - a system for composing music via Lisp code, heavily inspired by SuperCollider’s patterns system, with aims to implement much of it, but in a more robust, expressive, consistent, reflective, and lispy way. Audio output through SuperCollider, with preliminary support for Incudine, and MIDI through ALSA.
• cl-openal - bindings for the OpenAL audio library. Public domain.
• Common Music - the repository of an ancient version of Common Music (version 2.12.0), the presumably last version which ran on Common Lisp dating from around 2007-09, before work on Common Music shifted to (scheme-based) cm3.
• Slippery Chicken - Algorithmic composition library which outputs Midi, Common Music Notation, pdf-score via Lilypond and sound via Common Lisp Music. GPL3.
• Common Music Notation - Common Music Notation (CMN) provides a package of functions to hierarchically describe a musical score. Public domain.
• cm-incudine - extends Common Music 2 with realtime capabilities. GPL2.
• Mégra - A mini-language to make music with variable-order markov chains and some other stochastic shenanigans. GPL3.
• Music - A framework for musical expression in Lisp with a focus on music theory (built from scratch, unrelated to Common Music).
• rq - A library for rhythm transcription in OpenMusic (version 6.10 and later). demo video. GPL3.
• scheduler - The time based musical event scheduler for Common Lisp. Apache2.0.
• mixalot - Loosely-coupled collection of audio libraries for mp3, ogg vorbis, flac. Used for the Shuffletron music player. MIT.
• osc - an implementation of the Open Sound Protocol. LGPL2.1.
• Harmony - A real-time sound processing and playback system. zlib.

Build Systems

• ⭐ASDF - Another System Definition Facility; a build system for Common Lisp. Expat. Quicklisp (see library manager) uses ASDF under the hood.
  • known ASDF extensions, such as asdf-system-connections, that lets you specify systems that are automatically loaded when two other systems are loaded, to connect them.
• asdf-linguist - Extensions for ASDF. Expat.
• asdf-viz - a tool to visualize the library dependencies of ASDF systems, the call graph of a function and the class inheritances. LLGPL.

Compilers, code generators

APL

• April - The APL programming language (a subset thereof) compiling to Common Lisp. Replace hundreds of lines of number-crunching code with a single line of APL. Apache2.

C, C++

• cmacro - Lisp macros for C. MIT.
• C-mera - a source-to-source compiler that utilizes Lisp’s macro system for meta programming of C-like languages. GPL3.
• lispc - a powerful “lispsy” macrolanguage for C. MIT.
• with-c-syntax - a fun package which introduces the C language syntax into Common Lisp. (Yes, this package is not for practical coding, I think.) WTFPL Licence.
• ecrepl - an interactive REPL for the C language. BSD_2Clause.
• Software-Evolution-Library - The SEL enables the programmatic modification and evaluation of software (C/C++ support using Clang, compiled assembler, and linked ELF binaries). GPL3.

Cryptography

• ⭐ Ironclad - A library of crypto functions for Common Lisp. Not considered secure, but is still useful for the message digest functions. Expat.
• crypto-shortcuts - Collection of common crypto shortcuts. zlib.
• trivial-ssh - An SSH client library. Expat.
• cl-ssh-keys - Common Lisp system for generating and parsing of OpenSSH keys. BSD_3Clause.
• cl-bcrypt - Common Lisp system for parsing and generating bcrypt password hashes. BSD_3Clause.
  • see also cl-pass, using pbkdf2.

Cryptocurrencies

• cl-monero-tools - Common Lisp toolbox to work with the Monero cryptocurrency. GPL3. Not in Quicklisp.
• emotiq - a next-generation blockchain with an innovative natural-language approach to smart contracts. MIT.
• peercoin-blockchain-parser - parse the blockchain contained in a file and export some of its data to a text file, a SQL script or a database. It can also create a database using the RPC of a Peercoin daemon as source of data instead of a blockchain file. LGPL3. Not in Quicklisp.
• peercoin-calculator - This program gives you the probability of generating a POS or POW block within 10 minutes, 24 hours, 31 days, 90 days and 1 year, as well as the reward that can be expected. GUI in Qt. GPL3. Not in Quicklisp.
• peercoin-vote - A voting system based on data from the blockchain (addresses and balances). GPL3. Not in Quicklisp.

See also legochain, a simple educational blockchain.

Database

• cl-yesql - SQL statements live in their own files, in SQL syntax, and are imported into Lisp as functions. You are not limited to the features a DSL supports. Based on Clojure’s Yesql. MIT.

ORMs

• ⭐ clsql - An SQL database with a Common Lisp interface. LLGPL.
• 👍 mito - An ORM for Common Lisp with migrations, relationships and PostgreSQL support LLGPL. mitho-auth, a mixin class for use authorization; mito-attachment, a mixin class for file management outside of RDBMS.
• cl-dbi - A database-independent interface for Common Lisp. LLGPL.
  • dbd-oracle - an Oracle database driver for CL-DBI. LLGPL.
• crane - Another ORM. Expat.
• datafly - A lightweight database library. 3-clause BSD.
• sxql - A DSL for generating SQL. 3-clause BSD.

Persistent object databases

• bknr.datastore - a CLOS-based lisp-only database in RAM with transaction logging persistence. Manual. licence.
  • see also this good introductory blog post
  • an example web application using bknr.datastore: screenshotbot-oss.
• ubiquitous - A library providing easy-to-use persistent configuration storage. zlib.
• cl-prevalence - in-memory database system. Implementation of Object Prevalence, in which business objects are kept live in memory and transactions are journaled for system recovery. github fork. LLGPL. See also cl-prevalence-multimaster, to syncronize multiple cl-prevalence systems state.

See also Clache, that can save any object on disk.

Graph databases

• cl-agraph, a minimal client for AllegroGraph. AllegroGraph is a horizontally distributed, multi-model (document and graph), entity-event knowledge graph technology. It is proprietary and has a free version with a limit of 5 million triples.
• neo4cl - a library for interacting with Neo4J. Sends Cypher queries to a Neo4J server, and decodes the responses into something useful for processing in CL. Apache2.
  • and maybe: cl-neo4j - a thin neo4j RESTFUL client interface.
• vivace-graph - graph database & Prolog implementation. Takes design inspiration from CouchDB, neo4j and AllegroGraph. It implements an ACID-compliant object graph model with user-defined indexes and map-reduce views. It also implements a master / slave replication scheme for redundancy and horizontal read scaling. Querying the graph is accomplished via a number of Lisp methods or via a Prolog-like query language. MIT.
• facts - an in-memory graph database with transactions and rollbacks, logging/replay and dumping/loading to/from disk. BSD-style license (ISC).

and also:

• restagraph - an app that dynamically generates REST APIs for a Neo4j database, using a schema defined within the database. GPL3.

Wrappers

• ⭐ postmodern - A library for interacting with PostgreSQL. zlib.
• cl-sqlite - Bindings for SQLite. Public domain.
• cl-memcached - Fast, thread-safe interface to the Memcached object caching system. Expat.
• cl-mongo - MongoDB client. Expat.
• cl-redis - Redis client. Expat.
• cl-disque - Disque client. 3-clause BSD.
• cl-rethinkdb - RethinkDB client. Expat.
• cl-mango - A minimalist CouchDB 2.x database client. BSD_3Clause. See also clouchdb - Library for interacting with CouchDB. FreeBSD.
• lmdb - Bindings to LMDB, the Lightning Memory-mapped Database, an ACID key-value database with MultiVersion Concurrency Control.

Migration tools

• cl-migratum - a system which provides facilities for performing database schema migrations, designed to work with various databases. BSD_3Clause.
• postmodern-passenger-pigeon - a migration manager for postmodern. No licence specified.

To third parties

• dyna - an AWS DynamoDB ORM. MIT.
• cl-influxdb - an interface to the Time Series Database InfluxDB. MIT.
• pzmq - ZeroMQ 4.0+ Common Lisp bindings. Unlicense.

Tools

• pgloader - a data loading tool for PostgreSQL. PostgreSQL Licence.

Data Structures

• 👍 str - a modern, simple and consistent string manipulation library. MIT.
• 👍 FSet - A functional, set-theoretic collections data structure library. LLGPL.
• trivial-extensible-sequences - Portability library for the extensible sequences protocol (SBCL documentation). zlib.
• bst - Binary Search Tree. GPL3.
• pileup - a portable, performant, and thread-safe binary heap for Common Lisp. MIT.
• sycamore - a fast, purely functional data structure library. BSD_3Clause.
• genhash – hash table implementation with API from generic methods. Public domain.
• cl-ctrie - lock-free, concurrent, key/value index with efficient memory-mapped persistence and fast transient storage models. MIT.
• cl-data-structures - a portable collection of data structures and algorithms (mainly dicts and sequences, with some statistical functions). BSD.
• listopia - a list manipulation library inspired by Haskell’s Data.List. LLGPL.
• hash-set - a convenience library implementing hash sets on top of CL hash tables The Unlicense
• cl-containers - an extensive library of data structures and utilities - queues, trees, heaps, doubly-linked lists, sets, bags,… MIT
• cl-competitive - Common Lisp algorithms collection for competitive programming. Public domain, CCO or MIT.

Accessing data structures:

• 👍 access - Consistent and nested access to most common data structures. BSD_3Clause.
• modf - a setf-like macro for functional programming.

Other data structures:

• bitfield - Efficiently represent several finite sets or small integers as a single non-negative integer. MIT.

Docker images

• cl-docker-images - Docker images for ABCL, CCL, ECL, and SBCL on Windows (amd64) and Alpine and Debian (amd64, arm64, arm/v7) BSD_2Clause.
• base-lisp-image - base Docker image for Common Lisp projects with SBCL or CCL and the latest ASDF, Qlot and Roswell.

Foreign Function Interface, languages interop

C

• ⭐ CFFI - Portable, easy-to-use C foreign function interface. Expat.
• 👍cl-autowrap - Automatically parses header files into CFFI definitions. FreeBSD.
• cl-bindgen - A command line tool and library for creating Common Lisp language bindings from C header files. MIT.
• cl-gobject-introspection - Gobject Introspection FFI. Automatic bindings to call into the C library. BSD. Generate a lisp interface with gir2cl. LGPL3.
• cl-cxx-jit - Common Lisp and C++ interoperation with JIT. MIT.

Clojure

• ABCLJ - dead easy Clojure to Common lisp interop. EPL-2.0.

Erlang

• CLERIC - a Common Lisp Erlang Interface. An implementation of the Erlang distribution protocol, comparable with erl_interface and jinterface. MIT.

Java

• cl+j - A JNI-based interface to a JVM via CFFI. Not available on Quicklisp. Does not reliably work with all implementations. Expat.

Objective-C

• objc-lisp-bridge - A portable reader and bridge for interacting with Objective-C and Cocoa. MIT.

Python

• burgled-batteries - A bridge between Python and Common Lisp. The goal is that Lisp programs can use Python libraries. Not available on Quicklisp. MIT.
• cl4py - The library cl4py (pronounce as clappy) allows Python programs to call Common Lisp libraries. MIT.
• py4cl - A library that allows Common Lisp code to access Python libraries. It is basically the inverse of cl4py. MIT.
• cl-python - an implementation of Python in Common Lisp. LLGPL.

See also async-process.

.Net Core

• Bike - a cross-platform .Net Core interface. MIT.

Miscellaneous

• Foil - A foreign object interface; works with the JVM and CLI. Not available on Quicklisp. CPL 1.0.

Game Development

• Xelf - Extensible game library. Not available on Quicklisp. GNU LGPL2.1.
• Trial - Trial is an OpenGL game engine with a heavy focus on modularity. It is supposed to provide a large toolkit of useful bits and pieces from which you can create a game. zlib.
• cl-mpg123 and cl-out123, bindings libraries for libmpg123 and libout123 respectively, giving you fast and easy to use mp3 decoding and cross-platform audio output. zlib.
• trivial-gamekit – with this small framework you would be able to make simple 2D games: draw basic geometric forms, images and text, play sounds and listen to mouse and keyboard input. MIT.
• cl-gamepad - Access to gamepads and joysticks on Windows, Mac OS, and Linux. zlib.
• virality - A component-based game engine written in Common Lisp MIT.

Graphics

These are libraries for working with graphics, rather than making GUIs (i.e. widget toolkits), which have their own section.

• ⭐ Sketch - A CL framework for the creation of electronic art, graphics, and lots more. MIT.
• common-cv - the OpenCV (Open Source Computer Vision Library) binding library for CommonLisp. No license specified.
• cl-cairo2 - Cairo bindings. Boost 1.0
• cl-gd - A library providing an interface to the GD graphics library. FreeBSD.
• cl-horde3d - FFI bindings to the Horde3D graphics library. Not available on Quicklisp. EPL 1.0
• cl-jpeg - Baseline JPEG encoder and decoder library. 3-clause BSD.
• cl-liballegro - Interface and bindings to the Allegro 5 game programming library. zlib.
• cl-opengl - CFFI bindings to OpenGL, GLU and GLUT APIs. 3-clause BSD.
• cl-sdl2 - Bindings for SDL2 using C2FFI. Expat.
• cl-svg - A basic library for producing SVG files. Expat.
• CLinch - Common Lisp 2D/3D graphics engine for OpenGL. FreeBSD.
• donuts - Graph drawing DSL for Common Lisp. Expat.
• dufy - exact color manipulation and conversion in various color models. MIT.
• lispbuilder-sdl - A set of bindings for SDL. Expat.
• lisp-magick-wand - ImageMagick bindings. BSD. Not in Quicklisp.
• okra - CFFI bindings to Ogre. Not available on Quicklisp. 3-clause BSD.
• opticl - a library for representing and processing images. BSD_2Clause.
• Varjo - Lisp to GLSL translator. BSD_2Clause.
• Vecto - Simple vector drawing library. FreeBSD.
• zpng - A library for creating PNG files. FreeBSD.
• pngload-fast - A PNG (Portable Network Graphics) image format decoder in portable Common Lisp with an emphasis on speed. MIT.
• cl-cuda - A library to use NVIDIA CUDA in Common Lisp programs. LLGPL.

GUI

For an overview and a tutorial on GUI toolkits, see the Cookbook/GUI.

• LispWork’s CAPI - A portable GUI toolkit, with mobile runtime. Proprietary, but comes with a free version.
• Allegro’s Common Graphics- a library of functions for writing windowized GUIs for Windows, Mac and Linux. Proprietary with a free version.
  • since Allegro 10.1 (March, 2022), the IDE and the Common Graphics toolkit runs in the browser.
• 👍 Qtools - A Qt toolkit, based on CommonQt. zlib Also Qtools-ui (premade UI components), with videos.
• ⭐ CommonQt - A Common Lisp binding for Qt4 via QtSmoke. FreeBSD.
• ⭐ ltk - A binding for the Tk toolkit. LLGPL or GNU LGPL2.1.
  • LTk Examples - Provides LTk examples for the tkdocs tutorial.
  • LTk Plotchart - A wrapper around the tklib/plotchart library to work with LTk. This includes over 20 different chart types (xy-plots, gantt charts, 3d-bar charts etc…).
  • nodgui - Bindings for the Tk toolkit, based on Ltk, with syntax sugar and additional widgets. LLGPL.
• IUP - CFFI bindings to the IUP Portable User Interface library (pre-ALPHA). IUP is cross-platform (Windows, macOS, GNU/Linux, with new Android, iOs, Cocoa and Web Assembly drivers), has many widgets, has a small api and is actively developed.
• cl-cffi-gtk - Binding for GTK+3. GNU LGPL2.1.
  • a tutorial: Learn Common Lisp by Example: GTK GUI with SBCL
• cl-gtk2 - A binding for GTK+2. LLGPL.
• ceramic - Desktop web apps with Electron. Expat.
  • Electron-lisp-boilerplate - A rudimentary boilerplate for building Electron apps with embedded Lisp helper processes.
  • Electron app skeleton: electron-sbcl-sqlite

But that’s not all:

• CocoaInterface - Cocoa interface for Clozure Common Lisp. Build Cocoa user interface windows dynamically using Lisp code and bypass the typical Xcode processes. It has good documentation and a tutorial.
• McCLIM - An implementation of the Common Lisp Interface Manager, version II. GNU LGPL2.1.
• cl-webkit - A binding to WebKitGTK+. Also adds web browsing capabilities to an application, leveraging the full power of the WebKit browsing engine. MIT.
• ftw - A Win32 GUI library. MIT.
• eql, eql5, eql5-android - Embedded Qt4 and Qt5 Lisp, embedded in ECL, embeddable in Qt. Port of EQL5 to the Android platform. MIT.
• bodge-nuklear - Wrapper over the Nuklear immediate mode GUI library. MIT.
• vk - Common Lisp/CFFI bindings for the Vulkan API. MIT.

Other utilities:

• file-select - A library to invoke the native system file dialog to select or create files. Zlib.

See also this demo to use Java Swing from ABCL.

Mobile

• LispWork’s mobile runtime - Android and iOs. Proprietary.
• LQML - a lightweight ECL binding to QML (both Qt5 and Qt6) derived from EQL5. LGPL and public domain.

See also MOCL below, CL as a library for mobile devices (iOS, Android and OSX).

Implementations

• ⭐ SBCL - Steel Bank Common Lisp. A fork of CMUCL; compiles to machine code. Standard compliance. Public domain, with some parts under Expat and 3-clause BSD.
  • see also: sbcl-librarian - Dynamic library delivery tools for SBCL. MIT. Blog post. Full example.
• ⭐ CCL - Clozure Common Lisp; compiler-only implementation, generates native code. LLGPL.
• ECL - Embeddable Common Lisp; compiles to C. GNU LGPL2.1.
• ABCL - Armed Bear Common Lisp; targets the JVM, compiles to bytecode. Standard conformance. GNU GPL3 with Classpath exception.
• CLASP - a new Common Lisp implementation that seamlessly interoperates with C++ libraries and programs using LLVM for compilation to native code. This allows Clasp to take advantage of a vast array of preexisting libraries and programs, such as out of the scientific computing ecosystem. LGPL2.1 (and others).

Proprietary:

• LispWorks - an integrated cross-platform development tool for Common Lisp.
• Allegro CL - provides the full ANSI Common Lisp standard with many extensions.
• MOCL - CL as a library for mobile devices (iOS & Android) and OSX.

See also:

• CMUCL - An implementation from Carnegie Mellon University. Public domain. SBCL is a fork of CMUCL.
• GNU CLISP - A GNU implementation; contains a compiler and an interpreter. Standard conformance. GNU GPL3.
• Corman Lisp - a Common Lisp development environment for Microsoft Windows running on Intel platforms. MIT.

JSON

• jonathan - A JSON encoder and decoder. MIT.
• cl-json - A highly customizable JSON encoder and decoder. MIT.
• jsown - A reader and writer for the JSON format. Expat.
• json-mop - A metaclass for bridging CLOS and JSON objects. MIT.
• cl-json-pointer - A JSON Pointer implementation. MIT.

See also this extensive comparison of JSON libraries.

YAML

• cl-yacclyaml - a pure lisp YAML processor (loader, but not yet dumper). GPL3.
• cl-yaml - a YAML parser and emitter built on top of libyaml. MIT.

Language extensions

• ⭐ alexandria - A general-purpose utility library. Public domain.
• serapeum - Another general-purpose utility library. Expat.
• rutils - radical yet reasonable syntactic utilities for Common Lisp. MIT.
• anaphora - A collection of anaphoric macros. Public domain.
• ⭐ trivia - Optimized pattern-matching library. LLGPL.
• arrow-macros - Clojure-like threading macros. MIT.
• dissect - when a lot of projects use the “trivial-backtrace” system that just gives them a string with a backtrace, Dissect allows you to capture, step, and completely inspect the stack trace on a variety of Lisp implementations. Also very useful for logging and other situations where execution is automatically continued, but the information of the current stack is still useful to store somewhere. zlib.
• generic-cl - Generic function interface to standard Common Lisp functions (equality, comparison, arithmetic, objects, iterator, sequences,…). MIT. See also the more lightweight generic-comparability. LLGPL.
• hu.dwim.walker - a code walker and unwalker (aka AST parser and unparser). BSD. See also this blog post.

Portability layers

A large list of portability layers is collected here. Here are some of them:

• trivial-arguments - A portable library to retrieve the arguments list of a function. zlib.
• definitions - a general definitions introspection library. It gives you the ability to retrieve definitions or bindings associated with designators such as symbols, packages, and names in general. zlib.

Changing the syntax

• cl21 - An experimental project to move Common Lisp into the 21st century. Expat.
• clamp - Arc language’s brevity and conciseness to Common Lisp. Artistic License 2.0.
• cl-syntax - Reader syntax conventions. LLGPL.
• cl-2dsyntax - An indentation-sensitive reader system. Not available on Quicklisp. Public domain.
• cl-annot - Python-like annotations for Common Lisp. LLGPL.
• ⭐ cl-interpol - A set of reader modifications to allow string interpolation. BSD.
• pythonic-string-reader - A simple and unobtrusive read table modification inspired by Python’s three quote strings. BSD_3Clause.
• cl-reader - A utility library intended at providing reader macros for lambdas, mapping, accessors, hash-tables and hash-sets. MIT.

CLOS extensions

• ⭐ closer-mop - A compatibility layer that rectifies many absent or incorrect MOP features. Expat.
• defclass-std - a shortcut macro to write DEFCLASS forms quickly. LLGPL.
• specialization-store - generic functions based on types. Simplified BSD License variant.
• filtered-functions - enable the use of arbitrary predicates for selecting and applying methods. MIT.
• inlined-generic-function - Bringing the speed of Static Dispatch to CLOS. LLGPL.
• static-dispatch - allows standard generic function dispatch to be performed statically (at compile time) rather than dynamically (runtime). This is similar to what is known as “overloading” in languages such as C++ and Java. MIT.
• dynamic-mixins - simple, dynamic class combination. BSD_2Clause.
• fast-generic-functions - Seal your generic functions for an extra boost in performance. MIT.
• polymorphic functions - A function type to dispatch on types instead of classes with partial support for dispatching on optional and keyword argument types. Still experimental (May, 2021). MIT.
  • polymorphic-functions dispatch on the types of the arguments supplied to it. This helps dispatching on specialized arrays as well as user-defined types.
  • for differences with specialization-store and fast-generic-functions, see its README.

And also:

• slot-extra-options - lets you build a metaclass which in turn lets you specify extra slot options in its classes. LGPL3.

Function extensions

• cl-hooks - Hooks extension point mechanism (as known, e.g., from GNU Emacs). LGPL.
• method-hooks - When CLOS method combination allow only one hook per method, this library allows an arbitrary number of them. Mozilla Public Licence.
• cl-advice - an attempt of portable layer advice library for SBCL, CCL, LispWorks and Allegro. Not in Quicklisp.

See also hooks in Serapeum.

Iteration

• ⭐ iterate - An iteration construct for Common Lisp which is extensible and Lispier. MIT.
• for - A concise, lispy and extensible iteration macro. Unlike loop it is extensible and sensible, and unlike iterate it does not require code-walking and is easier to extend. zlib.
• series - Functional style without any runtime penalty at all. MIT.
• gmap - A concise and extensible iteration facility that has the advantage of integrating well with FSet (see the Data Structures section), as it was written by the same author. In Quicklisp as part of misc-extensions. Public domain.
• trivial-do - Additional dolist style macros for Common Lisp. MIT.
• doplus – another extensible iteration library, similar to :for.
• snakes - Python style generators for Common Lisp. Includes a port of itertools. Apache2.
• picl - An (almost) complete port of Python’s itertools package, complete with laziness where applicable, and not relying on cl-cont. MIT.
• gtwiwtg - A lazy sequences library. Similar to ‘series’ but not as complete. However it has a ‘modern’ API with stuff like take, filter, for, fold, etc. that is easy to use.

Lambda shorthands

• fn - a couple of lambda shorthand macros. (fn* (+ _ _)) --> (lambda (_) (+ _ _)). Public domain.
• f-underscore - a tiny library of functional programming utils. (f_ (+ _ _)) -> (lambda (_) (+ _ _)). Public domain.
• cl-punch - Scala-like anonymous lambda literals. (mapcar ^(* 2 _) '(1 2 3 4 5)). MIT.

See also CL21 and Rutils.

Non-deterministic, logic programming

• cl-prolog2 - Common Interface to ISO Prolog implementations from Common Lisp. MIT.
• Screamer - augment Common Lisp with practically all of the functionality of both Prolog and constraint logic programming languages. Blog post solving Project Euler puzzles. MIT.
• Screamer+ - increasing the expressiveness of SCREAMER. MIT.
• Temperance - logic programming. MIT. A focus on performance, with General Game Playing in mind.

Reactive programming

• Cells - an implementation of the dataflow programming paradigm, reactive spreadsheet-like expressiveness for CLOS. Used to build an algebra learning system. With documentation. Lisp LGPL.

Contract programming

• quid-pro-quo - a contract programming library in the style of Eiffel’s Design by Contract ™. Public domain.

Typing

• 👍 Coalton - an efficient, statically typed functional programming language that supercharges Common Lisp. MIT.
• cl-algebraic-data-type - A library for defining algebraic data types in a similar spirit to Haskell or ML. 3-clause BSD.
• 👍 trivial-types - provides missing but important type definitions such as proper-list, association-list, property-list and tuple. LLGPL.
• defstar - a collection of macros for easy inclusion of type declarations for arguments in lambda lists. GNU GPL3

Learning and Tutorials

Online

Beginner

• Learn X in Y minutes - Where X = Common Lisp - Small Common Lisp tutorial covering the essentials.
• Lisp Koans - The project guides the learner progressively through many Common Lisp language features.
• Practical Common Lisp - A good introductory text to Common Lisp, with practical examples. Better read with a Firefox add-on.
• Common LISP: A Gentle Introduction to Symbolic Computation - A nice introduction into the language.
• Successful Lisp - A good book for beginners with some programming background.
• Lisp Quickstart - A good tutorial to get up and code Common Lisp quickly.
• Casting SPELs in LISP - A fun way to learn LISP while reading a comic book.
• 📹 Common Lisp Programming: from novice to effective developer - A learning video series on the Udemy platform (full content under paid access). Teaches the language basics, explains the ecosystem and shows real-world examples. By an active lisper and community contributor (@vindarel).

  Thanks for supporting my work on Udemy. Also note that I release free coupons from time to time, and that Udemy often proposes drastic promotions, but you can ask me a free coupon too.

Intermediate

• The Common Lisp Cookbook
• Lisp Tips - A blog with useful tips and tricks. A continuation of Common Lisp tips.
• Lisp project of the day - A blog showcasing many Lisp libraries.

Advanced

• Let Over Lambda - A book on advanced macro techniques. The first six chapters are available online.
• On Lisp - Paul Graham’s amazing book on Lisp macros (and other interesting things).
• Programming Algorithms in Lisp - Updated version of “Programming Algorithms”; A comprehensive guide to writing efficient programs with data structures and algorithms in Lisp.

Web Development

• Lisp for the Web - A book that walks you through building a voting web application in three tiers.
• Lisp Web Tales - Simple tutorials using hunchentoot, cl-redis, restas, SEXML, Postmodern, and more.
• Section on Web Development in The Common Lisp Cookbook - An introductory tutorial covering web server setup, routing, weblocks, templating, error handling, packaging, hot reloading, database connection, and deployment, amongst other topics in the current lisp web development ecosystem.

Reference

• Common Lisp Quick Reference - A distilled, pocket-size version of the ANSI CL spec. Available for download as a PDF.
• CLHS - The Common Lisp HyperSpec; the ANSI CL standard, in hypertext form.
• CLOS MOP specification - A modern public domain online version of chapters 5 and 6 of The Art of the Metaobject Protocol
• Common Lisp Standard Draft (pdf) - The standard draft of the Common Lisp specifications, in a well formatted PDF with a sidebar.
• Common Lisp the Language - The original standard for Common Lisp before the ANSI spec.
• Minispec - A friendlier, but less-complete, version of CLHS. Also contains documentation for some commonly-used CL libraries (such as Alexandria).
• Simplified Common Lisp reference - The simplified version of CLHS.
• CDR - Common Lisp Document Repository. a repository of documents that are of interest to the Common Lisp community. The most important property of a CDR document is that it will never change: if you refer to it, you can be sure that your reference will always refer to exactly the same document.
  • the Common Lisp Document Repository is hosted at Zenodo.

Offline

The CLHS is available offline via an archive and as doc sets in Dash, Zeal and Velocity.

Beginner

• Land of Lisp - A fun, game-oriented introduction to Common Lisp.
• Practical Common Lisp - A good introductory text to Common Lisp, with practical examples.

Intermediate

• ANSI Common Lisp - A thorough, practical covering of the entire language, with exercises. Not recommended as a starter text, due to some caveats.
• Common Lisp Recipes - Common Lisp Recipes is a collection of solutions to problems and answers to questions you are likely to encounter when writing real-world applications in Common Lisp. Published in 2015.

Advanced

• Let Over Lambda - A book on advanced macro techniques. All eight chapters are available in the print copy.
• Object-Oriented Programming in Common Lisp: A Programmer’s Guide to CLOS - An old, but very thorough book on CLOS.
• Paradigms of Artificial Intelligence Programming: Case Studies in Common Lisp - A book on programming AI that covers some advanced Lisp.

Other books

• Building Problem Solvers (PDF) by Ken Forbus and Johan de Kleer, made available for free by MIT Press - a unique book among standard artificial intelligence texts in combining science and engineering, theory and craft to describe the construction of AI reasoning systems, and including code illustrating the ideas.

Community

• /r/Common_Lisp - subreddit about Common Lisp
• /r/learnlisp - a subreddit to ask questions and get help about Lisp
• common-lisp.net
• lisp-lang.org
• Lisp Discord Server
• #commonlisp on Libera Chat - main Common Lisp IRC channel.
• #lisp on Libera Chat - IRC channel for all Lisp dialects.
• #clschool on Libera Chat - IRC channel for learning Common Lisp.
• #lispcafe on Libera Chat - IRC channel for off-topic discussions.
• Planet Lisp - A meta blog that collects the contents of various Lisp-related blogs.
• Common Lisp chat - Keybase team with well-defined rules and retention policies.

Library Manager

• ⭐ Quicklisp - A library manager containing many libraries, with easy depencency management. Expat.
• CLPM - A package manager for Common Lisp that strives to cleanly separate the package manager process itself from the client image that uses it. BSD_2Clause.
• Ultralisp - A Quicklisp distribution which updates every 5 minutes and to which one can add his project in one click. BSD.
• 👍Roswell - a Lisp implementation installer, script launcher and more. MIT.
• Qlot - A project-local library installer, similar to Bundler or Carton. Expat.
• Quicksys - install systems from multiple Quicklisp distributions. MIT.
• Quickutil - A utility manager, similar to Quicklisp, but for small utilities rather than whole libraries. 3-clause BSD.

might help:

• quick-patch - easily override quicklisp projects without using git submodules. MPL-2.0.
• print-licenses - print licenses used by a project and its dependencies. MIT.

Interfaces to other package managers

• linux-packaging - build .deb, .rpm or .pkg packages for your application with a single ASDF declaration. Uses fpm under the hood. MIT.
• qldeb - Quicklisp systems to debian packages, along with deb-packager (simply create a debian package by defining an s-expression) and an introductory blog post. Both MIT.
• ql-to-deb - Update cl-* debian packages from Quicklisp releases. WTFPL.
• dh-quicklisp-buildapp - debhelper utility to let you compile your quicklisp-based Common Lisp code into a buildapp binary in a .deb with almost no effort. MIT.
• cl-brewer - Homebrew formula builder for (command line) common lisp applications. Public domain.
• flatpack-common-lisp - A BuildStream project for building Flatpak based runtime environments for Common Lisp applications.

See also asdf-sbcl, a plugin for the universal package manager.

Machine Learning

• MGL - a machine learning library for backpropagation neural networks, boltzmann machines, gaussian processes and more. MIT.
  • some parts originally contributed by Ravenpack International.
  • used by its author to win the Higgs Boson Machine Learning Challenge.
• clml - originally developed by Mathematicl Systems Inc., a Japanese company. With a tutorial. LLGPL.
• antik - a foundation for scientific and engineering computation in Common Lisp. GPL. Also mgl-mat and LLA.

Credit: borretti.me’ state of CL ecosystem 2015.

Natural Language Processing

• cl-nlp - Natural language processing toolset. Apache2.0.
• babel2 - A Fluid Construction Grammar implementation, computational framework, and unification-based grammar formalism Apache2.0.
• sparser - A natural language understanding system for English. Eclipse.

Network and Internet

See Cliki for more.

HTTP clients

• 👍 Dexador - An HTTP client, that aims at replacing Drakma. MIT.
• Carrier - A lightweight, async HTTP client built on top of cl-async and fast-http. MIT.
• fast-http - A fast HTTP request/response parser for Common Lisp. MIT.

HTTP Servers

• 👍Clack - A web application environment inspired by Rack and WSGI. LLGPL. Provides a unified interface to a webserver of choice (default is Hunchentoot). With more getting started guide.
• ⭐ Hunchentoot - A web server. 2-clause BSD
• zaserve - A portable fork of AllegroServe, by Franz Inc. LLGPL.
• wookie - Asynchronous HTTP server. Expat.
• woo - A fast non-blocking HTTP server on top of libev. MIT.
• cl-http2-protocol - a pure Common Lisp transport agnostic implementation of the HTTP/2 protocol at draft-14. MIT.

Hunchentoot plugins

• 👍 easy-routes - a routes handling system on top of Hunchentoot. It supports dispatch based on HTTP method, arguments extraction from the url path, decorators, url generation from route name, etc. MIT.
• hunchentoot-cgi - a library for executing CGI scripts from the hunchentoot webserver. BSD.
• hunchentoot-multi-acceptor - Route multiple domains (virtual hosts) on a single hunchentoot acceptor using a single port. Apache2.0.
• hunchentoot-auth - implementing user authentication with passwords. BSD.
• hunchentoot-errors - Augments Hunchentoot error pages and logs with request and session information. MIT.

Clack plugins

• clack-errors - Error page middleware for Clack. LLGPL.
• clath - a single sign-on middleware for Clack. It allows basic login with OAuth1.0a, OAuth2 and OpenID. At the time of writing, it supports authentication from Google, Twitter, LinkedIn, StackExchange, Reddit and Github. Apache2.0.
• clack-pretend - a testing and debugging tool for clack. Apache2.0.
• hermetic - Security for Clack-based web applications. Expat.
• live-reload - Live reload prototype for clack. LLGPL.
• clack-static-asset-middleware - a cache-busting static asset middleware for the clack. MIT.

Web frameworks

• Caveman - A powerful web framework. LLGPL. Example projects: Quickdocs
• ningle - A super-micro web framework. LLGPL. ninglex, an extended and noob-friendly ningle (mostly easier handling of query parameters). MIT.
• radiance - A web application environment and framework . zlib.

REST-focused frameworks:

• 👍 Snooze - A RESTful web framework. Web server agnostic. Currently has support for Hunchentoot and Clack. Routes are just functions and HTTP conditions are just Lisp conditions. LLGPL.
• cl-rest-server - a library for writing REST web APIs. Features validation with schemas, annotations for logging, caching, permissions or authentication, documentation via Swagger, etc. MIT.
• cl-odata-client - Common Lisp client library for accessing OData services. MIT.

Authentication plugins (in addition to the Clack plugins above):

• cl-cas - A library to help CAS authenticaton to Common Lisp web applications. Not in Quicklisp.
  • cas-middleware - CAS authenticaton middleware for Caveman.
  • cas-demo - a demo project.

There are more projects, more or less discontinued but interesting. See the other resources.

Isomorphic web frameworks

• CLOG - The Common Lisp Omnificent GUI. Uses web technology to produce graphical user interfaces for applications locally or remotely. BSD_3Clause.
  • CLOG is based on the ideas of GNOGA, a framework the author wrote for Ada and used in commercial production code since 2013.
• Interactive SSR - ISSR allows you to make interactive web pages without writing client scripting. No knowledge about Javascript or DOM is necessary.
  • it is not unlike Phoenix LiveView or Hotwire.
• Weblocks - A widgets-based framework with a built-in ajax update mechanism that “solves the JavaScript problem”. LLGPL.

Assets management

• Rock - an asset manager for Common Lisp. It’s basically a combination of Bower and webassets. MIT.

Parsing html

• 👍 Plump - A lenient HTML/XML parser, tolerant on malformed markup. zlib. Best used with lquery and clss.

Querying HTML/DOM

• 👍 lquery - A jQuery-like HTML/DOM manipulation library. zlib.

See also the XML section below for xpath libraries and more.

HTML generators and templates

• 👍 spinneret - Common Lisp HTML5 generator. Expat.
• ⭐ cl-who - The venerable HTML generator. FreeBSD.
• ⭐ Djula - A port of Django’s template engine to Common Lisp. Expat.
• eco - Fast, flexible, designer-friendly template engine. Expat.
• TEN - the completness of Djula meets the usability of Eco. MIT.
• cl-closure-template - Implementation of Google’s Closure templates. LLGPL.
• flute - An easily composable HTML5 generation library with the most simplistic syntax. MIT.
• clip - An HTML template processor where the templates are written in HTML. zlib.
• lsx and markup - Two JSX-like templating engines, where HTML tags are Common Lisp code. markup comes with an Emacs package.

URI handling

• quri - Another URI library for Common Lisp. Supports userinfo, IPv6 hostname, encoding/decoding utilities,… BSD_3Clause.
• cl-slug - a small library to make slugs, mainly for URIs, transform in CamelCase, remove accentuation and punctuation, for english and beyound. LLGPL.

Javascript

• ⭐ Parenscript - A translator from Common Lisp to Javascript. 3-clause BSD. See Trident-mode, an Emacs mode that provides live interaction with the browser.unlicence.
  • paren6 - a set of ES6 macros for Parenscript.
• parse-js - A package for parsing ECMAScript 3. zlib.
• JSCL - A CL-to-JS compiler designed to be self-hosting from day one. Lacks CLOS, format and loop.
• CL-JavaScript - A translator from Javascript to Common Lisp. Not available on Quicklisp. Expat.
• Wuwei - A toolkit to build Ajax-based web pages. MIT.
• SmackJack - An Ajax Common Lisp Library using parenscript to generate javascript and hunchentoot (for now) as the web server. Also allows a server-side lisp function to call a client-side parenscript one. MIT.
• remote-js - send JavaScript from Common Lisp to a browser. MIT.
• sigil - A Parenscript to Javascript command line compiler and REPL. MIT.

Utilities for React:

• cl-react - Common Lisp (Parenscript) utilities for building web apps in ReactJs. MIT.
• Panic, a Parenscript library for React. Not in Quicklisp. MIT. Its TodoMVC example.
• Parenscriptx - Parenscript Macros to aid generating react code. MIT.
• jscl-react - A web framework for writing react components in common lisp using jscl. No license specified.

See also:

• trident-mode, an Emacs minor mode for live Parenscript interaction.

Email

• trivial-imap - tries to make easy some common cases of working with IMAP servers, like reading emails from the server. A thin wrapper over post-office library (which is a fork of Franz’s cl-imap). BSD.
• mailgun - A thin wrapper to post HTML emails through mailgun.com. unlicence.
• mito-email-auth - Helper to authenticate a website’s users by sending them unique code by email.
• cl-smtp - CL-SMTP is a simple lisp smtp client.

Websockets

• 👍 usocket - A portable TCP and UDP socket interface. Expat.
• websocket-driver - a WebSocket server/client implementation, backend agnostic (Clack). 3-clause BSD.
• Portal - Portable websockets for Common Lisp using usocket. LLGPL.

See more on cliki.

Static site generators

• coleslaw and its coleslaw-cli - Flexible Lisp Blogware similar to Frog, Jekyll, or Hakyll. BSD.

Deployment

• heroku-buildpack-common-lisp - A Heroku buildpack that uses Roswell to compile Common Lisp applications. LGPL3.
• cube - Kubernetes client library for Common LISP generated from the Swagger specification. MIT.
• s2i-lisp - Source-to-Image builder image based on CentOS or alternatively RHEL7 for building Common LISP images for OpenShift (and also Docker). It features an up-to-date SBCL with Quicklisp installation, SLIME or SLY integration and allows customization via environment variables. Apache2
• deploy - A toolkit for binary deployment of Lisp applications, with extra support for foreign shared libraries. zlib.
• cl-aws-runtime-test - An example of using Common Lisp (SBCL) as a custom runtime on AWS lambda. WTFPL.

See also:

• Platform.sh has Common Lisp support, so has OVH through their Web PaaS partnership.
• Heliohost for a free hosting solution.

Monitoring

• prometheus.cl - Prometheus.io client. Grafana dashboard for SBCL and Hunchentoot metrics (memory, threads, requests per second,…). MIT.
• cl-sentry-client - a Sentry client for Common Lisp, the cloud-based error monitoring system. MIT.
• rollbar.lisp - interface to Rollbar.com, an error tracking software.

Third-party APIs

• Aws-sign4 - Common Lisp library for Amazon Web Services signing version 4. GNU GPL3.
• zs3 - A library for working with Amazon’s Simple Storage Service (S3) and CloudFront service. BSD.
• cl-ses - Library for AWS SES. Expat.
• north - The successor to the South (Simple OaUTH) library, implementing the full oAuth 1.0a protocol, both client and server sides. Using North you can easily become an oAuth provider or consumer. zlib.
• avatar-api - Get avatars from Google+, Gravatar and others. Expat.
• chirp - A Twitter client library. zlib.
• tooter - a client library implementing the full v1 REST API protocol for Mastodon. zlib.
• cl-irc - An IRC client library. Expat.
• cl-mediawiki - a wrapper around the MediaWiki api. MIT.
• cl-openid - An implementation of OpenID. LLGPL.
• cl-pushover - Common Lisp bindings to Pushover. MIT.
• humbler - A Tumblr API interface. zlib.
• multiposter - post to multiple services simultaneously. zlib.
• stripe - a client for the Stripe payment system. MIT.

Web project skeletons and generators

• cl-cookieweb - a Cookiecutter template to start a web project. BSD_3Clause. Not in Quicklisp.
  • Provides a working toy web app with the Hunchentoot web server, easy-routes, Djula templates, styled with Bulma, based on SQLite, with migrations, an example table definition and a test suite using FiveAM.
• make-like - an application template builder for LIKE (Lisp In Kubernetes + Emacs) applications. Apache2.0.
  • Makefile, podman support, GitHub Actions, Prometheus metrics support, TOML-style config.ini, easy-route preconfigured with health-check and more.
• cl-webapp-seed - a simple web application boilerplate. Uses Hunchentoot, cl-who, deploys easily to Heroku. MIT.

Others

• 👍 cl-forms - Web forms handling library for Common lisp. MIT.
• maiden - A bot and chat system framework with support for IRC and more. zlib.
• css-lite - A CSS grammar. Expat.
• find-port - Programmatically find open ports. MIT.
• Postmaster - A simple, easy-to-use SMTP/IMAP library. Expat.
• cl-webdriver-client - a binding library to WebDriver (supports Selenium 4.0).
• cl-wget - Makes retrieving large files or mirroring entire websites easy. AGPL-3.0.
• trivial-download - Download files. MIT.

Numerical and Scientific

• numcl - Numpy clone in Common Lisp. LGPL3.
• GSLL - GNU Scientific Library for Lisp; allows the use of the GSL from Common Lisp. GNU LGPL2.1.
• maxima - Computer algebra system. Not available on Quicklisp. GNU GPL3.
• Xecto - A library for regular array parallelism. 3-clause BSD.
• Petalisp - an attempt to generate high performance code for parallel computers by JIT-compiling array definitions. It works on a more fundamental level than NumPy, by providing even more powerful N-dimensional arrays, but just a few building blocks for working on them. AGPL-3.0.
• cl-ana - Common Lisp data analysis library with emphasis on modularity and conceptual clarity. It aims to be a general purpose framework for analyzing small and large scale datasets, including binned data analysis and visualization. GNU GPL3.
• linear-programming – a library for solving linear programming problems. MIT.
• avm - Efficient and expressive arrayed vector math library with multi-threading and CUDA support. MIT.
• array-operations - a collection of functions and macros for manipulating Common Lisp arrays and performing numerical calculations with them. MIT.
• cl-geometry - a system for two dimensional computational geometry for Common Lisp. MIT.
• Vellum - Data Frames for Common Lisp. BSD_2Clause.
• rtg-math - a selection of the math routines most commonly needed for making realtime graphics in lisp (2, 3 and 4 component vectors, 3x3 and 4x4 matrices, quaternions, spherical and polar coordinates). BSD_2Clause.
• origin - A native Lisp graphics math library with an emphasis on performance and correctness. Includes: vectors, matrices (up to 4x4), quaternions, single/double-float support, destructive/non-destructive operations, shaping & intersections. MIT.

Matrix libraries

• magicl - Matrix Algebra proGrams In Common Lisp based on BLAS/LAPACK and Expokit, by Rigetti Computing. BSD_3Clause.
• lisp-matrix - A matrix package. FreeBSD.
• 3d-matrices - A library implementing common matrix calculations, with an emphasis on 2x2,3x3, and 4x4 matrices as commonly used in graphics. It provides some numerical functions as well, but those are not the focus. The library is heavily optimised, so it is not made of pretty code. zlib.
• clem - a matrix library. BSD_2Clause.

Statistics

• lisp-stat - an environment for statistical computing, conceptually similar to R, that is also suitable for front-line production deployments. “It grew out of a desire to have an environment for rapidly prototyping analytical and A.I. solutions, and move directly to production environments with minimal friction.”
  • https://lisp-stat.dev/
  • ships Luke Tierney’s XLisp-Stat (a predecessor of R) as well as newer libraries.
• common-lisp-stat - Common Lisp statistics library. FreeBSD.

Units

• physical-quantities - a library that provides a numeric type with optional unit and/or uncertainty for computations with automatic error propagation. GPL2

Utils

• cmu-infix - A library for writing infix mathematical notation in Common Lisp. See also polisher.

Parallelism and Concurrency

• ⭐ BordeauxThreads - Portable, shared-state concurrency. Expat.
• ⭐ lparallel - A library for parallel programming. 3-clause BSD.
• lfarm - distributing work across machines (on top of lparallel and usocket). BSD_3Clause
• calispel - CSP-like channels for common lisp. With blocking, optionally buffered channels and a “CSP select” statement. ISC-style.
  • “It is complete, flexible and easy to use. I would recommend Calispel over Lparallel and ChanL.” @Ambrevar. discussion
• chanl - Portable, channel-based concurrency. Expat, with parts under 3-clause BSD.
• cl-async - A library for general-purpose, non-blocking programming. Expat.
• Moira - Monitor and restart background threads. In-lisp process supervisor. MIT.
• trivial-monitored-thread - a Common Lisp library offering a way of spawning threads and being informed when one any of them crash and die. MIT.
• cl-gearman - a library for the Gearman distributed job system. LLGPL.
• swank-crew - distributed computation framework implemented using Swank Client. BSD_3Clause.
• cl-coroutine - a coroutine library. It uses the CL-CONT continuations library in its implementation. MIT.
• STMX - High performance Transactional Memory for Common Lisp. LLGPL.

See also:

• cl-etcd - Run etcd as an asynchronous inferior process. etcd is a strongly consistent, distributed key-value store. AGPL-3.0.

Actors pattern

• 👍 cl-gserver - cl-gserver is a ‘message passing’ library/framework with actors similar to Erlang or Akka. It supports creating systems that should work reactive, require parallel computing and event based message handling. Apache2.
• erlangen - Distributed, asynchronous message passing system for Clozure Common Lisp. GNU GPL3.
• Actors package for LispWorks (announce) MIT.
• common-lisp-actors - a simple and easy to use Actor system. BSD_2Clause.
• memento-mori- a library for writing robust, actor-based systems. It draws inspiration from Erlang/OTP, particularly its crash-first approach to high-availability systems, as well as Akka. MIT.

Event processing

• simple-tasks - A very simple task scheduling framework. zlib.
• deeds - Deeds is an Extensible Event Delivery System. It allows for efficient event delivery to multiple handlers with a complex event filtering system. zlib.
• cl-flow - Data-flowish computation tree library for non-blocking concurrent Common Lisp. MIT.
• event-glue - simple eventing abstraction. No dependencies. It can be used anywhere you need a generic event handling system. MIT.

Job processing

• SBCL’s timers, system-wide event schedulers.
• psychiq - redis-based background job processing for Common Lisp applications. Inspired by Ruby’s Sidekiq and compatible with its web UI. LLGPL.
• cl-cron - A simple tool that provides cron like facilities. GPL3.
• clerk - a cron-like scheduler with sane DSL. MIT.

Regex

• ⭐ cl-ppcre - Portable, Perl-compatible regular expressions. FreeBSD.
• one-more-re-nightmare - a fast-ish regular expression compiler in Common Lisp. BSD_2Clause.

Scripting

Writing, running scripts

• 👍 Roswell - a lisp installer and scripting environment (helper, launcher, installer) and more. MIT.
• cl-all - A script to run Lisp snippets in multiple implementations. This allows you to quickly compare implementation behaviour and differences. zlib.
• clawk - an AWK implementation embedded into Common Lisp, to search files for lines and perform specified actions on its fields. BSD-style.
• ScriptL - Shell scripting made Lisp-like! Or, live-coding remote function calls for the shell. Write a command in the REPL, and run it instantly in the shell. LLGPL.
  • similar and maybe simpler: lserver

Command-line options parsers

• 👍 Unix-opts - a command line options parser with a concise declaration of options. MIT.
• Adopt - A Damn OPTion parsing library. MIT.
• Clingon - a rich command-line options parser system.
  • newer, it may have the richest feature set: subcommands, generation of bash completion, support for various kinds of options (integers, booleans, counter, enums…), extensible…

Readline, ncurses and other graphical helpers

• cl-readline - a set of functions to edit lines as they are typed in, to maintain a list of previously-entered command lines, to recall and reedit them and perform csh-like history expansion. Emacs and vi editing modes. GPL3.
• Linedit - Readline-style library that provides customizable line-editing features. MIT-style.
• cl-charms - an interface to libcurses in Common Lisp. It provides both a raw, low-level interface to libcurses via CFFI, and a more higher-level lispier interface. MIT.
• replic - helpers to turn existing code into a readline application, with a focus on defining the completion of the commands’ arguments. Also comes as a ready to use executable, that transforms a user’s lispy init file into readline commands. MIT.
• cl-ansi-term - print colorized text, horizontal lines, progress bars, (un)ordered lists and tables on ANSI-compliant terminals. GPL3.
• cl-progress-bar - progress bars, just like in Quicklisp ! MIT.

Shells, shells interfaces

• Lish - lish may someday be a lisp shell. GPL3.
  • supports tab-completion of executables in the path and Lisp symbols, allows to write and to mix shell commands and Lisp code, has a tiny REPL and an interactive debugger, and more.
• shcl - a POSIX-like shell in Common Lisp. Apache2.0.
• Shelly - execute Common Lisp functions like a shell command, without the need to write a command line arguments parser. And it also can be used as a Make-like build-tool. FreeBSD.
• cmd - utility for running external programs. Protects against shell interpolation, built with multi-threaded programs in mind, Windows support. MIT.
  • uiop:run-program (synchronous) and uiop:launch-program (async) are shipped with ASDF and available on all modern implementations. See the CL Cookbook: running external programs.
• Clesh - extends Common Lisp to embed shell code in a manner similar to perl’s backtick. FreeBSD.

System administration

• Consfigurator - Lisp declarative configuration management system. You can use it to configure hosts as root, deploy services as unprivileged users, build and deploy containers, and produce disc images. GPL3.
• Adams - UNIX system administration in Common Lisp. Not unlike Ansible, Chef or Puppet. ISC.

Other scripting utilities

• WCL [staled] - allow hundreds of Lisp applications to be realistically available at once, while allowing several of them to run concurrently. WCL accomplishes this by providing Common Lisp as a Unix shared library that can be linked with Lisp and C code to produce efficient applications. For example, the executable for a Lisp version of the canonical Hello World! program requires only 20k bytes on 32 bit x86 Linux. WCL also supports a full development environment, including dynamic file loading and debugging. A modified version of GDB is used to debug WCL programs, providing support for mixed language debugging.

Text Editor Resources

This contains plugins and other goodies for various text editors.

• Parinfer - Parinfer is a way to edit lisp code that helps to keep both the indentation and the parenthesis balanced. It is easy to start with and yet it offers advanced features à la Paredit. It is available on many editors (Emacs, Vim, Neovim, Atom, Sublime Text, Visual Studio Code, LightTable, CodeMirror,…).

Emacs

• ⭐ Slime - Superior Lisp Interaction Mode for Emacs; a full-blown environment for Common Lisp inside of Emacs. Public domain.
• 👍 Sly - SLY is a fork of SLIME and contains multiple improvements upon it.
• 👍 Portacle - A portable and multiplatform Common Lisp environment: SBCL, Quicklisp, Emacs, Slime, Git.
• cl-devel2 - a Docker container for Common Lisp development environment. Ships SBCL, CCL, Roswell and Emacs25 with Slime.
• Emacs4CL - A tiny Emacs initialization file to quickly set up vanilla Emacs for Common Lisp programming. Comes with a line-by-line explanation of every line of code in the initialization file.
• slime-star - a SLIME configuration with extensions pre-installed, with also some custom utilities and menus:
  • the Lisp system browser
  • SLIME doc contrib - enhance the default help buffer.
  • Quicklisp systems - Search, browse and load Quicklisp systems from Emacs.
  • Quicksearch
  • Slime breakpoints
  • Slite - a test runner for FiveAM.

Vim & Neovim

• SLIMV - Superior Lisp Interaction Mode for Vim; a full-blown environment for Common Lisp inside of Vim. No license specified.
• Vlime - VLIME: Vim plus Lisp Is Mostly Evil. A Common Lisp dev environment for Vim (and Neovim). MIT.
• quicklisp.nvim - A Quicklisp frontend for Neovim.
• Slimv_box - slimv in a Docker container.

Eclipse

• Dandelion - a Common Lisp plugin for the Eclipse IDE.

Lem

• Lem - a ready to use, Emacs-like, Slime-based editor tailored for Common Lisp development out of the box, as well as other programming languages. With ncurses and Electron interfaces. MIT. See also: an opengl frontend, Lem in Docker, lem-pareto.

Atom

• SLIMA allows you to interactively develop Common Lisp code, turning Atom into a pretty good, and actively developped, Lisp IDE. MIT.

Sublime Text

• Sublime Text (proprietary) has Common Lisp support with its SublimeREPL and Slyblime packages. Slyblime is an implementation of SLY and it uses the same backend (SLYNK). It ships advanced features including a debugger with stack frame inspection.

VSCode

• commonlisp-vscode - an extension to support syntax highlight, auto completion, documentation on hover, go to definition, compile & load file, REPL. It is On GitHub.
• alive - Common Lisp Extension for VSCode. Public domain.
  • see the Cookbook: using VSCode with Alive
• strict-paredit-vscode - structural editing and navigation like Emacs.

Geany (experimental)

• Geany-lisp is an experimental lisp mode for the Geany editor.

Notebooks

• cl-jupyter - A Common Lisp kernel for Jupyter notebooks custom licence.
• common-lisp-jupyter - A Common Lisp kernel for Jupyter along with a library for building Jupyter kernels, based on Maxima-Jupyter by Robert Dodier which was based on cl-jupyter by Frederic Peschanski. MIT.
• Darkmatter - A notebook-style Common Lisp environment. MIT.

REPLs

• cl-repl - an ipython-like REPL. With completion, shell commands, magic commands, debugger, etc. MIT. With colorthemes.
• sbcli - a readline REPL for SBCL. With completion, quick commands, optional syntax highlighting (with pygments), and no interactive debugger. GPL3.
• magic-ed - a tiny editing facility, where you can directly load, edit, manipulate and evaluate file or file content from the REPL, when going to a full IDE is too much. MIT.

Online editors

• Judge0 IDE is an online editor which supports Common Lisp (SBCL). MIT.

Apps

• CodePlayground - an iPhone and iPad app with Lisp support via CCL.

Text Parsers

• ⭐ esrap - Packrat parser. Expat.
• cl-yacc - a LALR(1) parser generator. MIT.
• cl-shlex - simple lexical analyzer for shell-like syntaxes. MIT.
• smug - parser combinators for Common Lisp. SMUG makes it simple to create quick extensible recursive descent parsers without funky syntax or impenetrable macrology. MIT.
• parseq - a library for parsing sequences such as strings and lists using parsing expression grammars. Inspired by Esrap. GPL2.
• texp - A DSL to generate TeX. AGPL-3.0.

Text Processing

• montezuma - Full-text indexing and search for Common Lisp. Expat.
• mk-string-metrics - Calculate various string metrics efficiently in Common Lisp (Damerau-Levenshtein, Hamming, Jaro, Jaro-Winkler, Levenshtein, etc). MIT.
• wiki-lang-detect - Text language identification using Wikipedia data. No license specified.
• cl-phonetic - Phonetic pattern matching library for Common Lisp (intended to replace the Sylvia library for Python). MIT.
• cl-string-generator - Generate string from regular expression. MIT.

Tools

These are applications or bits of code that make development in Common Lisp easier without being Common Lisp libraries themselves.

• quicksearch - Look up online libraries from the REPL. Expat.
• lake - a GNU make like build utility. MIT.

Unit Testing

• ⭐ FiveAM - Simple regression testing framework. FreeBSD.
• CLUnit2 - A unit testing library. MIT.
• Parachute - An extensible and cross-compatible testing framework. With test dependencies, conditions, fixtures and restarts. zlib.
• Mockingbird - A small stubbing and mocking library for Common Lisp. Can also check wether a stubbed function was called, how many times and with which arguments. MIT.
• cl-mock - Another mocking library. It has more features than Mockingbird, like pattern matching on the mocked call, etc.
• Check-it - A QuickCheck-style randomized property-based testing. LLGPL.
• cl-coveralls - a helper library to post test coverage to Coveralls. See SBCL’s code coverage tool. FreeBSD.

Editor utilities:

• Slite - a SLIme-based TEst runner for FiveAM Tests. Apache2.0
  • Slite interactively runs your Common Lisp tests (at the time of writing only FiveAM is supported). It allows you to see the summary of test failures, jump to test definitions, rerun tests with the debugger, all from inside Emacs.

Utilities

Caching

• clache - General caching facility. Cache any Lisp object on disk or in memory. A cache can be persistent or have an expiration time. LLGPL.

Compression / decompression

• chipz - A decompression library. 3-clause BSD.
• Salza2 - A library for creating compressed data. FreeBSD.
• zippy - A ZIP archive format library based on 3bz. zlib.

Configuration

• 👍 py-configparser - reads and writes Python’s ConfigParser-like configuration files. MIT.
• envy - Configuration switcher. FreeBSD.
• chameleon - a configuration management library shipped with profile support. MIT.

CSV

• ⭐ cl-csv - A library for parsing CSV files. 3-clause BSD.
• cl-decimals - Decimal number parser and formatter. Public domain.
• auto-text - automatic (encoding, end of line, column width, csv delimiter etc) detection for text files. MIT. See also inquisitor for detection of asian and far eastern languages.

Date and time

• ⭐ local-time - A development library for manipulating date and time information in a semi-standard manner. 3-clause BSD.
• cl-date-time-parser - Parse date-time-string, liberally. Hides the difference between date-time formats, and enables to manage date and time as the one date-time format. MIT.
• chronicity - A natural language date and time parse, to parse strings like “3 days from now”. BSD_3Clause.
• local-time-duration - Duration processing library built on top of local-time. MIT.
  • see this fork: humanize-duration, that outputs only significant parts of a duration object. Has localization suport.
• iso-8601-date - Miscellaneous date routines in Common Lisp, based around the ISO 8601 string representation. LLGPL.
• calendar-date - a Gregorian calendar date library. MIT.
• periods - manipulating date/time objects at a higher level. With series-compatible data structure. BSD_3Clause.

See also the book Calendrical calculations, by Edward M. Reingold, Nachum Dershowitz, Cambridge Press. It provides Lisp sources.

Data validation

• ratify - A collection of utilities to ratify, validate and parse inputs. zlib.
• clavier - General purpose validation library for Common Lisp. MIT.
• json-schema - A library for validating data against schemas of drafts 4, 6, 7, and 2019-09 of the JSON Schema standard. LLGPL.
• sanity-clause - a data serialization/contract library for Common Lisp. Schemas can be property lists or class-based, allowing to check slots’ types during make-instance. LLGPL.

Developer utilities

• repl-utilities - Ease common tasks at the REPL (print documentation, print external symbols, call hooks when loading a package,…). BSD_2Clause.
• flight-recorder - a robust REPL history facility.
• tracer - tracing profiler for Common Lisp, with output suitable for display in Chrome’s/Chromium’s Tracing Viewer. MIT.
• cl-flamegraph - A wrapper around SBCL’s statistical profiler, to generate FlameGraph charts for Common Lisp programs. BSD.
• cl-debug - a cross-package debug facility. Provides a unified way to enable or disable debug-specific code. Debugging code can be enabled or disabled relative to program features denoted by either a symbol or a keyword. ISC licence.
• supertrace - Superior Common Lisp trace functionality for debugging/profiling. Trace many functions at once, use before and after hooks. BSD_2Clause.
• printv - A batteries-included tracing and debug-logging macro. Apache2.
• journal - a library for logging, tracing, record-and-replay testing and persistence. MIT.

and also:

• GTFL - A graphical terminal for Lisp, meant for Lisp programmers who want to debug or visualize their own algorithms. A graphical trace in the browser. BSD-style.
• trivial-with-current-source-from - Helps macro writers produce better errors for macro users. GPL3.
• trivial-benchmark - Tiny benchmarking library. zlib.
• glyphs - A library for cutting down the verboseness of Common Lisp in places. GNU GPL3.
• Lisp REPL core dumper - A portable wrapper to generate Lisp cores on demand to start REPL blazing fast. It can preload provided systems to help build a collection of specialized Lisp cores.

Documentation builders

• Staple - a tool to generate documentation pages using an HTML template. Uses the existing README, adds docstrings, crossreferences and links to the CLHS. zlib.
• mgl-pax - Exploratory programming environment and documentation generator. one may accomplish similar effects as with Literate Programming, but documentation is generated from code, not vice versa. Code is first, code must look pretty, documentation is code. MIT.
  • see this 40ants fork for: a lighter core system, a JavaScript search index, multiple format output, HTML themes, RSS and Atom feed for the Changelog and more.
• Declt - Reference manual generator for Common Lisp libraries. Builds a texinfo document that can be further processed into various formats, such as HTML or PDF. BSD.
• Codex - A beautiful documentation system for Common Lisp. MIT.
• QBook - generates HTML (or LaTeX) formatted code listings of Common Lisp source files. BSD_3Clause.
  • all comments started with 4 ; (“;;;;”) are interpreted as documentation. Enhance the documentation with headings and directives.
  • QBook acts as “a lightweight literate programming system, where Lisp code is not rendered inline, but in separate sections, and that makes the document more pleasant to navigate.” @mmontone
• sphinxcontrib-cldomain - Extending Sphinx to cover Common Lisp. To build documentation with the same ease as sphinx would a Python project. GPL3
• cl-bibtex - A compatible re-implementation of the BibTeX program in Common Lisp, with a BST-to-CL compiler. GNU LGPL2.1.

See also:

• docbrowser - a server that generates documentation for the loaded systems on the fly.
  • Its main page presents a list of all loaded systems in your Lisp image. Click on one system, and you get a page with three panes: functions, classes and variables. Click on a function to see its source, in context, with line numbers. Click on classes to see their slots and specializing functions.

An overview blog post with even more documentation generators: https://lisp-journey.gitlab.io/blog/overview-of-documentation-generators/

You might also like: literate programming systems.

Files and directories

• ⭐ uiop and its pathname package (replaces cl-fad). uiop is part of ASDF3 and as thus is shipped in many implementations. MIT.
• osicat - A lightweight operating system interface on POSIX-like systems (directory iteration and deletion, environment variables, file permissions, etc) Expat.
• pathname-utils - A collection of utilities to help with pathname operations. zlib.
• ppath - Common Lisp’s implementation of the Python’s os.path module. BSD.
• archive - a library for reading and creating archive (tar, cpio) files. BSD_3Clause. A pure Common Lisp replacement for the tar program.
  • see its recent fork cl-tar (2021). Announce.
• mmap - Portable mmap file memory mapping utility library. zlib.
• fof - File-object finder Common Lisp library. Enable rapid file search, inspection and manipulation. GPL3.

File watching libraries:

• cl-inotify - interface to the Linux inotify API. Simplified BSD License.
• cl-fswatch - an CFFI wrapper of fswatch, a cross-platform file change monitor. ISC.

Git

• legit - an interface to the Git binary. zlib.
• git-api - Common Lisp library to access git repository. It doesn’t need git or libgit installed. BSD.

i18n

• cl-i18n - an i18n library. Load translations from GNU gettext text or binary files or from its native format. Localisation helpers of plural forms. LLGPL.
• gettext - a port of the gettext runtime to Common Lisp. GPL3.
• translate - seamless language localization. LLGPL.
• enchant - bindings for the Enchant spell-checker library. Public domain.
• oxenfurt - A client library for the Oxford dictionary API. zlib.
• language-codes - A database library for ISO language codes. zlib
• system-locale - A library to retrieve the user’s preferred language, so that your application may choose a sensible default. zlib.
• multilang-documentation - Allows writing docstrings in multiple languages, for truly internationally documented libraries. zlib.

Linting, code formatting

• sblint - a linter for Common Lisp source code using SBCL, suited for Reviewdog (slides). BSD_2Clause.
• trivial-formatter - code formatter for Common Lisp. MIT.

and also: lisp-format and cl-indentify.

Literate programming

• literate-lisp - Load Common Lisp code blocks from Emacs’ Org files. MIT.
• erudite - Literate Programming System built with interactive development in mind. MIT.

Logging

• ⭐ log4cl - Logging framework modelled after Log4J. Apache2.0. Advanced integration with Slime.
  • log4cl-json - JSON appender extension. BSD.
• verbose - A fast and highly configurable logging framework. zlib.
• a-cl-logger - Logging library providing context sensitive logging of more than just strings to more than just local files or output streams. Features logstash support, json support, logger hierarchies, context sensitive logging, objects printed as an inspectable presentation,…

To third parties:

• cl-fluent-logger - A Common Lisp structured logger for Fluentd.

See also: extensive comparison of logging libraries.

Markdown

• 3bmd - a markdown -> html converter. MIT.

PDF

• cl-typesetting and cl-pdf - cross-platform Common Lisp libraries for generating PDF files. FreeBSD.
• cl-pslib - a (thin) wrapper around the pslib library for generating PostScript files. Also cl-pslib-barcode. LLGPL.

Plotting

• vgplot - an interface to the gnuplot plotting utility with the intention to resemble some of the plot commands of octave or matlab. GPL3.
• eazy-gnuplot - a lispy, structure-less Gnuplot library. With its cookbook. LLGPL
• kai - A high-level plotter library for Common Lisp. A wrapper around the Plotly JS library. MIT.
• ADW-Charting - A simple chart drawing library written completely in Common Lisp. Also includes a backend to Google’s chart service. BSD-like.
• cl-spark - sparkline strings for the console: (spark '(1 1 2 3 5 8)) => “▁▁▂▃▅▇”. MIT.

See also the chart facilities of IUP and ltk-plotchart (GUI section).

Project skeletons

• cl-project - General modern project skeletons. LLGPL.
• cl-project-with-docs - uses Sphinx and reStructured text to render nice and readable HTML documentation. BSD.
• cl-cookieproject - Generate a ready-to-use Common Lisp project. Not in Quicklisp. BSD_3Clause.
  • test definitions, entry point to run from sources, build a binary, Roswell integration…

Security

• cl-isolated - A restricted environment for Common Lisp code evaluation AGPL-3.0.

XML

• CXML - XML parser and serializer, with a range of extension libraries. LLGPL.
  • 👍 has an incremental parser, allowing to parse big files.
  • see the FXML fork, with fixes and new features. You should use it if your are parsing potentially ill-formed or malicious XML, or if you need to use Klacks with namespaces.
• Plump - A lenient XML parser. zlib.
• xpath (homepage - Implementation of the XML Path Language (XPath) Version 1.0. BSD_2Clause.
• s-xml - A basic parser. LLGPL.
• xmls - A small, simple, non-validating XML parser. 3-clause BSD.
• cl-feedparser - A Common Lisp (RSS, Atom) feed parser. LLGPL
• Buildnode - A common lisp library to ease interaction with CXML-dom, such as building Excel spreadsheets. BSD.

Other

This contains anything which doesn’t fit into another category.

• babel - A charset encoding/decoding library. Expat.
• corona - Create and manage virtual machines from Common Lisp http://eudoxia.me/corona MIT.
• fast-io - Fast octet-vector/stream I/O. 3-clause BSD.
• iolib - I/O library. Expat.
• named-readtables - Provides a readtable namespace, akin to package namespaces. 3-clause BSD.
• simple-currency - A currency conversion library using daily information published by the ECB. FreeBSD.
• trivial-garbage - A portable finalizer, weak hash-table and weak pointer API. Public domain.
• trivial-utf8 - A small library for doing UTF-8-based I/O. BSD.

Contributing

Your contributions are always welcome! Please submit a pull request or create an issue to add a new framework, library or software to the list.

The rules we (try to) respect are the followings:

• by default, add a library to the end of its section.
• absolute de-facto libraries, like BordeauxThreads or Quicklisp, should be denoted with a ⭐ (Unicode code U+2B50).
• two libraries very similar in scope should be side by side, or in a section of their own.
• do some curation based on your experience and the state of the library’s documentation. We do not aim at listing every existing CL library (see Cliki for that) nor to list every “popular” library (see Quicklisp stats).
• as such, the libraries we like best are marked with a 👍 (1F44D unicode character). See also the signs’ explanation in the introduction.