9front: draft port. WIP.
Update state header to include pthread
Simplify eval.
Janet is a functional and imperative programming language and bytecode interpreter. It is a lisp-like language, but lists are replaced by other data structures (arrays, tables (hash table), struct (immutable hash table), tuples). The language also supports bridging to native code written in C, meta-programming with macros, and bytecode assembly.
There is a REPL for trying out the language, as well as the ability to run script files. This client program is separate from the core runtime, so Janet can be embedded in other programs. Try Janet in your browser at https://janet-lang.org.
If you'd like to financially support the ongoing development of Janet, consider sponsoring its primary author through GitHub.
Janet makes a good system scripting language, or a language to embed in other programs. It's like Lua and Guile in that regard. It has more built-in functionality and a richer core language than Lua, but smaller than GNU Guile or Python.
Documentation is also available locally in the REPL.
Use the (doc symbol-name)
macro to get API
documentation for symbols in the core library. For example,
(doc apply)
Shows documentation for the apply
function.
To get a list of all bindings in the default
environment, use the (all-bindings)
function. You
can also use the (doc)
macro with no arguments if you are in the REPL
to show bound symbols.
You can get the source on GitHub or SourceHut. While the GitHub repo is the official repo, the SourceHut mirror is actively maintained.
The Makefile is non-portable and requires GNU-flavored make.
cd somewhere/my/projects/janet
make
make test
make repl
make install
make install-jpm-git
Find out more about the available make targets by running make help
.
32-bit Haiku build instructions are the same as the UNIX-like build instructions,
but you need to specify an alternative compiler, such as gcc-x86
.
cd somewhere/my/projects/janet
make CC=gcc-x86
make test
make repl
make install
make install-jpm-git
FreeBSD build instructions are the same as the UNIX-like build instructions,
but you need gmake
to compile. Alternatively, install directly from
packages, using pkg install lang/janet
.
cd somewhere/my/projects/janet
gmake
gmake test
gmake repl
gmake install
gmake install-jpm-git
NetBSD build instructions are the same as the FreeBSD build instructions.
Alternatively, install directly from packages, using pkgin install janet
.
build_win
to compile janet.build_win test
to make sure everything is working.To build an .msi
installer executable, in addition to the above steps, you will have to:
build_win dist
Now you should have an .msi
. You can run build_win install
to install the .msi
, or execute the file itself.
Janet also has a build file for Meson, a cross-platform build system. Although Meson has a Python dependency, Meson is a very complete build system that is maybe more convenient and flexible for integrating into existing pipelines. Meson also provides much better IDE integration than Make or batch files, as well as support for cross-compilation.
For the impatient, building with Meson is as follows. The options provided to
meson setup
below emulate Janet's Makefile.
git clone https://github.com/janet-lang/janet.git
cd janet
meson setup build \
--buildtype release \
--optimization 2 \
--libdir /usr/local/lib \
-Dgit_hash=$(git log --pretty=format:'%h' -n 1)
ninja -C build
# Run the binary
build/janet
# Installation
ninja -C build install
Janet can be hacked on with pretty much any environment you like, but for IDE lovers, Gnome Builder is probably the best option, as it has excellent meson integration. It also offers code completion for Janet's C API right out of the box, which is very useful for exploring. VSCode, Vim, Emacs, and Atom will have syntax packages for the Janet language, though.
See the Introduction for more details. If you just want
to try out the language, you don't need to install anything. You can also move the janet
executable wherever you want on your system and run it.
A REPL is launched when the binary is invoked with no arguments. Pass the -h flag
to display the usage information. Individual scripts can be run with ./janet myscript.janet
If you are looking to explore, you can print a list of all available macros, functions, and constants
by entering the command (all-bindings)
into the REPL.
$ janet
Janet 1.7.1-dev-951e10f Copyright (C) 2017-2020 Calvin Rose
janet:1:> (+ 1 2 3)
6
janet:2:> (print "Hello, World!")
Hello, World!
nil
janet:3:> (os/exit)
$ janet -h
usage: build/janet [options] script args...
Options are:
-h : Show this help
-v : Print the version string
-s : Use raw stdin instead of getline like functionality
-e code : Execute a string of janet
-r : Enter the REPL after running all scripts
-p : Keep on executing if there is a top-level error (persistent)
-q : Hide prompt, logo, and REPL output (quiet)
-k : Compile scripts but do not execute (flycheck)
-m syspath : Set system path for loading global modules
-c source output : Compile janet source code into an image
-n : Disable ANSI color output in the REPL
-l path : Execute code in a file before running the main script
-- : Stop handling options
If installed, you can also run man janet
to get usage information.
Janet can be embedded in a host program very easily. The normal build
will create a file build/janet.c
, which is a single C file
that contains all the source to Janet. This file, along with
src/include/janet.h
and src/conf/janetconf.h
can be dragged into any C
project and compiled into the project. Janet should be compiled with -std=c99
on most compilers, and will need to be linked to the math library, -lm
, and
the dynamic linker, -ldl
, if one wants to be able to load dynamic modules. If
there is no need for dynamic modules, add the define
-DJANET_NO_DYNAMIC_MODULES
to the compiler options.
See the Embedding Section on the website for more information.
See the examples directory for some example janet code.
Feel free to ask questions and join the discussion on the Janet Gitter Channel. Gitter provides Matrix and irc bridges as well.
It may exist, it may not. If you want to propose major language features, go ahead and open an issue, but they will likely by closed as "will not implement". Often, such features make one usecase simpler at the expense of 5 others by making the language more complicated.
There is not currently a spec besides the documentation at https://janet-lang.org.
Nope. There are no cons cells here.
No. It's similar to Clojure superficially because I like Lisps and I like the aesthetics. Internally, Janet is not at all like Clojure.
No. They are immutable arrays and hash tables. Don't try and use them like Clojure's vectors and maps, instead they work well as table keys or other identifiers.
To some extent, yes. However, it is not the recommended method of abstraction, and performance may suffer. That said, tables can be used to make mutable objects with inheritance and polymorphism, where object methods are implemeted with keywords.
(def Car @{:honk (fn [self msg] (print "car " self " goes " msg)) })
(def my-car (table/setproto @{} Car))
(:honk my-car "Beep!")
Usually, one of a few reasons:
Make sure your terminal supports ANSI escape codes. Most modern terminals will
support these, but some older terminals, Windows consoles, or embedded terminals
will not. If your terminal does not support ANSI escape codes, run the REPL with
the -n
flag, which disables color output. You can also try the -s
if further issues
ensue.
Janet is named after the almost omniscient and friendly artificial being in The Good Place.