This document will guide you through setting up Fennel on your computer. This document assumes you know how to run shell commands and edit configuration files in a UNIX-like environment.
Note: Fennel can be used in non-UNIX environments, but those environments will not be covered in this document.
Downloading Fennel on your computer allows you to run Fennel code and compile to Lua. You have a few options for how to install Fennel.
Downloading the fennel script allows you to place the script in
convenient locations for running Fennel code.
This method assumes you have Lua 5.1, 5.2, 5.3, 5.4, or LuaJIT installed on your system.
This method requires you to manually update the fennel script when
you want to use a newer version that has come out.
- Download the fennel script
- Run
chmod +x fennel-0.9.2to make it executable - Download the signature
- Run
gpg --verify fennel-0.9.2.ascto verify that the fennel script is from the Fennel creators (optional but recommended) - Move
fennel-0.9.2to a directory on your$PATH, such as/usr/local/bin
Note: You can rename the script to fennel for convenience. Or
you can leave the version in the name, which makes it easy to keep
many versions of Fennel installed at once.
Downloading a Fennel binary allows you to run Fennel on your computer without having to download Lua, if you are on a supported platform.
This method requires you to manually update the fennel binary when
you want to use a newer version that has come out.
- Choose one the options below, depending on your system:
- Run
chmod +x fennel-0.9.2*to make it executable (not needed on Windows). - Download the signature and confirm it matches using
gpg --verify fennel-0.9.2*.asc(optional but recommended). - Move the downloaded binary to a directory on your
$PATH, such as/usr/local/bin
If you already use a package manager on your system, you may be able to use it to install Fennel. See the wiki for a list of packaging systems which offer Fennel.
Fennel code can be embedded inside of applications that support Lua either by including the Fennel compiler inside of the application, or by performing ahead-of-time compilation. Embedding Fennel in a program that doesn't already support Lua is possible but outside the scope of this document.
Note: Embedding the Fennel compiler in an application is the more flexible option, and is recommended. By embedding the Fennel compiler in an application, users can write their own extension scripts in Fennel to interact with the application, and you can reload during development. If the application is more restricted, (for instance, if you can only embed one Lua file into the application and it cannot load further files) then compiling Fennel code to Lua during the build process and including the Lua output in the application may be easier.
The Fennel compiler can be added to your code repository, and then loaded from Lua.
- Get the
fennel.lualibrary. You can get this from a release tarball or by runningmakein a source checkout. - Add
fennel.luato your code repository. - Add the following lines to your Lua code:
local fennel = require("fennel")
table.insert(package.loaders or package.searchers, fennel.searcher)
local mylib = require("mylib") -- will compile and load code in mylib.fnlBe sure to use the fennel.lua library and not the file for the
entire fennel executable.
If the target system of your application does not make it easy to add
the Fennel compiler but has Lua installed, Fennel offers ahead-of-time
compilation. This allows you to compile .fnl files to .lua files
before shipping an application.
This section will guide you through updating a Makefile to perform
this compilation for you.
-
Add the following lines to your
Makefile:%.lua: %.fnl fennel ./fennel --compile $< > $@ -
Ensure your build target depends on the
.luafiles you need.
Note 1: Ahead-of-time compilation is also useful if what you are working with requires optimal startup time. "Fennel compiles fast, but not as fast as not having to compile." -- jaawerth
Note 2: It's recommended you include the fennel script in your
repository to get consistent results rather than relying on an
arbitrary version of Fennel that is installed on your machine at the
time of building.
You can write Fennel code in any editor, but some editors make it more comfortable than others. Most people find support for syntax highlighting, automatic indentation, and delimiter matching convenient, as working without these features can feel tedious.
Other editors support advanced features like an integrated REPL, live reloading while you edit the program, documentation lookups, and jumping to source definitions.
If your favorite editor isn't listed here, that's OK; stick with what you're most comfortable. You can usually get decent results by telling your editor to treat Fennel files as if they were Clojure or Scheme files.
Installing fennel-mode gives you syntax highlighting, indentation, paren-matching, a repl, reloading, documentation lookup, and jumping to source definitions.
For more information, see the fennel-mode readme.
The fennel.vim plugin offers syntax highlighting and indentation support.
- For syntax highlighting and indentation, install fennel.vim
- To spin up a REPL in the terminal buffer, you can install a REPL plugin like iron.nvim and follow the documentation to add fennel as an executable REPL command.
Search in the built-in extension manager for "Fennel" to install the vsc-fennel extension. At the time of this writing it only provides syntax highlighting.
- The plugins based on lisp-parkour offer structured editing/navigation, automatic indentation, and (very) basic REPL integration.
- Vis and Textadept come with syntax highlighting for Fennel built in.
The command-line REPL that comes with the fennel script works out of the box, but
the built-in line-reader is very limited in user experience. Adding
GNU Readline
support enables user-friendly features, such as:
- tab-completion on the REPL that can complete on all locals, macros, and special forms
- a rolling history buffer, which can be navigated, searched (
ctrl+r), and optionally persisted to disk so you can search input from previous REPL sessions - Emacs (default) or vi key binding emulation via readline's custom support for better line navigation
- optional use of additional readline features in
~/.inputrc, such as blinking on matched parentheses or color output (described below)
- GNU Readline (installation steps vary for different operating systems, but you may already have it!)
- readline.lua Lua bindings to libreadline
Note: The Fennel REPL will automatically load and use the
readline bindings when it can resolve the readline module, so that's
all you need to get started.
The easiest way to get readline.lua is to install it with LuaRocks, which will fetch the package and automatically compile the native bindings for you.
To install readline.lua with LuaRocks:
- Ensure libreadline is installed for the Lua version you intend to use.
- Run one of the following commands:
luarocks install --local readline(recommended)luarocks install --lua-version=5.1 readline(for a non-default Lua version)luarocks install readline(requires root or admin)
Note: If you've installed with the --local flag, you may need to
ensure your package.path and package.cpath contain its location.
You can configure readline.lua using one of the following options:
- the readline.lua API in
fennelrc - the readline.lua
~/.inputrcfile
If you have readline installed but do not wish to use it (for example,
running Fennel inside an Emacs shell or recording a session to a file)
you can export TERM=dumb as an environment variable.
To configure the REPL to save the rolling history to file at the end of every
session, add the following to your fennelrc with your desired filename:
See the readline.lua documentation for information on its API, most notably other parameters that can be set via rl.set_options.
; persist repl history
(match package.loaded.readline
rl (rl.set_options {:histfile "~/.fennel_history" ; default:"" (don't save)
:keeplines 1000})) ; default:1000See the documentation on the readline init file for the full set of options and a sample inputrc.
The following example adds these behaviors:
- Blink on a matching parenthesis when entering
). Useful in a Lisp REPL, where the parens are plentiful! - Enable bracketed paste mode for more reliable pasting from clipboard
- When tab-completing on a term with more than one possible match, display all
candidates immediately instead of ringing the bell + requiring a second
<tab>
Create a ~/.inputrc file with the following contents:
set enable-bracketed-paste on
set blink-matching-paren on
set show-all-if-ambiguous onAs of Fennel 0.4.0 and readline.lua 2.6, you can make use of a conditional
directive your inputrc
if you would like certain settings to only apply to Fennel.
The two main platforms for making games with Fennel are TIC-80 and LÖVE.
TIC-80 is software that acts as a simulated computer in which you can write code, design art, compose music, and lay out maps for games. TIC-80 also makes it easy for you to publish and share the games you make with others. TIC-80 introduces restrictions such as low resolution and limited memory to emulate retro game styles.
LÖVE is a game-making framework for the Lua programming language. Because Fennel compiles to Lua, you can reference the LÖVE wiki when making games with Fennel. LÖVE is more flexible than TIC-80 in that it allows you to import from external resources and use any resolution or memory you like, but at a cost in that it is more complicated to make games in.
Both TIC-80 and LÖVE offer cross-platform support across Windows, Mac, and Linux systems, but TIC-80 games can be played in the browser and LÖVE games cannot.
The Fennel wiki links to many games made in both systems you can study.
Support for Fennel is built into TIC-80. If you want to use the
built-in text editor, you don't need any other tools, just launch
TIC-80 and run new fennel to get started.
The TIC-80 wiki documents the functions to use and important concepts.
All TIC-80 games allow you to view and edit the source and assets. Try loading this Conway's Life game to see how it's made:
- Click "start" to begin
- Press the Esc key and click "Close game"
- Press Esc again to see the code
LÖVE has no built-in support for Fennel, so you will need to setup support yourself, similar to Embedding Fennel above.
This project skeleton for LÖVE shows you how to setup support for Fennel and how to setup a console-based REPL for debugging your game while it runs.