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.
chmod +x fennel-1.1.0
to make it executablegpg --verify fennel-1.1.0.asc
to verify that the fennel script is from the Fennel creators (optional but recommended)fennel-1.1.0
to a directory on your $PATH
, such as /usr/local/bin
Note: You can rename the script to fennel
for convenience. Or you can leave the version in the name, which makes it easy to keep many versions of Fennel installed at once.
Downloading a Fennel binary allows you to run Fennel on your computer without having to download Lua, if you are on a supported platform.
This method requires you to manually update the fennel
binary when you want to use a newer version that has come out.
chmod +x fennel-1.1.0*
to make it executable (not needed on Windows).gpg --verify fennel-1.1.0*.asc
(optional but recommended).$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.
There are so many ways to distribute your code that we can’t cover them all here; please see the wiki page on distribution for details.
The Fennel compiler can be added to your code repository, and then loaded from Lua.
fennel.lua
library. You can get this from a release tarball or by running make
in a source checkout.fennel.lua
to your code repository.local fennel = require("fennel")
table.insert(package.loaders or package.searchers, fennel.searcher)
local mylib = require("mylib") -- will compile and load code in mylib.fnl
You can pass options to the fennel compiler, by using fennel.makeSearcher()
instead of fennel.searcher
.
Be 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 .lua
files 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.
See the wiki for a list of editors that have Fennel support.
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:
ctrl+r
), and optionally persisted to disk so you can search input from previous REPL sessions~/.inputrc
, such as blinking on matched parentheses or color output (described below)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:
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:
fennelrc
~/.inputrc
fileIf 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.
fennelrc
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:1000
~/.inputrc
See the documentation on the readline init file for the full set of options and a sample inputrc.
The following example adds these behaviors:
)
. Useful in a Lisp REPL, where the parens are plentiful!<tab>
Create a ~/.inputrc
file with the following contents:
set enable-bracketed-paste on
set blink-matching-paren on
set show-all-if-ambiguous on
As 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:
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.