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**Janet** is a functional and imperative programming language and bytecode interpreter. It is a
modern lisp, but lists are replaced
by other data structures with better utility and performance (arrays, tables, structs, tuples).
The language also bridging 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 could be embedded into other programs. Try janet in your browser at
[https://janet-lang.org](https://janet-lang.org).
#
Implemented in mostly standard C99, janet runs on Windows, Linux and macOS.
The few features that are not standard C (dynamic library loading, compiler specific optimizations),
are fairly straight forward. Janet can be easily ported to new platforms.
For syntax highlighting, there is some preliminary vim syntax highlighting in [janet.vim](https://github.com/janet-lang/janet.vim).
Generic lisp syntax highlighting should, however, provide good results. One can also generate a janet.tmLanguage
file for other programs with `make grammar`.
## Use Cases
Janet makes a good system scripting language, or a language to embed in other programs. Think Lua or Guile.
## Features
* Minimal setup - one binary and you are good to go!
* First class closures
* Garbage collection
* First class green threads (continuations)
* Python style generators (implemented as a plain macro)
* Mutable and immutable arrays (array/tuple)
* Mutable and immutable hashtables (table/struct)
* Mutable and immutable strings (buffer/string)
* Lisp Macros
* Byte code interpreter with an assembly interface, as well as bytecode verification
* Tailcall Optimization
* Direct interop with C via abstract types and C functions
* Dynamically load C libraries
* Functional and imperative standard library
* Lexical scoping
* Imperative programming as well as functional
* REPL
* Parsing Expression Grammars built in to the core library
* 300+ functions and macros in the core library
* Embedding Janet in other programs
* Interactive environment with detailed stack traces
## Documentation
Documentation can be found in the doc directory of
the repository. There is an introduction
section contains a good overview of the language.
API documentation for all bindings can also be generated
with `make docs`, which will create `build/doc.html`, which
can be viewed with any web browser. This
includes all forms in the core library except special forms.
For individual bindings from within the REPL, use the `(doc symbol-name)` macro to get API
documentation for the core library. For example,
```
(doc doc)
```
Shows documentation for the doc macro.
To get a list of all bindings in the default
environment, use the `(all-symbols)` function.
## Installation
Install a stable version of janet from the [releases page](https://github.com/janet-lang/janet/releases).
Janet is prebuilt for a few systems, but if you want to develop janet, run janet on a non-x86 system, or
get the latest, you must build janet from source. Janet is in alpha and may change
in backwards incompatible ways.
## Usage
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 0.0.0 alpha Copyright (C) 2017-2018 Calvin Rose
janet:1:> (+ 1 2 3)
6
janet:2:> (print "Hello, World!")
Hello, World!
nil
janet:3:> (os.exit)
$ ./janet -h
usage: ./janet [options] scripts...
Options are:
-h Show this help
-v Print the version string
-s Use raw stdin instead of getline like functionality
-e 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)
-- Stop handling option
$
```
## Embedding
The C API for Janet is not yet documented but coming soon.
Janet can be embedded in a host program very easily. There is a make target `make amalg`
which creates the file `build/janet.c`, which is a single C file that contains all the source
to Janet. This file, along with `src/include/janet/janet.h` can 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.
## Compiling and Running
Janet only uses Make and batch files to compile on Posix and windows
respectively. To configure janet, edit the header file src/include/janet/janet.h
before compilation.
### macos and Unix-like
On most platforms, use Make to build janet. The resulting binary will be in `build/janet`.
```sh
cd somewhere/my/projects/janet
make
make test
```
After building, run `make install` to install the janet binary and libs.
Will install in `/usr/local` by default, see the Makefile to customize.
It's also recommended to set the `JANET_PATH` variable in your profile.
This is where janet will look for imported libraries after the current directory.
### FreeBSD
FreeBSD build instructions are the same as the unix-like build instuctions,
but you need `gmake` and `gcc` to compile.
```
cd somewhere/my/projects/janet
gmake CC=gcc
gmake test CC=gcc
```
### Windows
1. Install [Visual Studio](https://visualstudio.microsoft.com/thank-you-downloading-visual-studio/?sku=Community&rel=15#)
or [Visual Studio Build Tools](https://visualstudio.microsoft.com/thank-you-downloading-visual-studio/?sku=BuildTools&rel=15#)
2. Run a Visual Studio Command Prompt (cl.exe and link.exe need to be on the PATH) and cd to the directory with janet.
3. Run `build_win` to compile janet.
4. Run `build_win test` to make sure everything is working.
### Emscripten
To build janet for the web via [Emscripten](https://kripken.github.io/emscripten-site/), make sure you
have `emcc` installed and on your path. On a linux or macOS system, use `make emscripten` to build
`janet.js` and `janet.wasm` - both are needed to run janet in a browser or in node.
The JavaScript build is what runs the repl on the main website,
but really serves mainly as a proof of concept. Janet will run slower in a browser.
Building with emscripten on windows is currently unsupported.
## Examples
See the examples directory for some example janet code.
## Discussion
Feel free to ask questions and join discussion on the [Janet Gitter Channel](https://gitter.im/janet-language/community).
Alternatively, check out [the #janet channel on Freenode](https://webchat.freenode.net/)
## Why Janet
Janet is named after the almost omniscient and friendly artificial being in [The Good Place](https://en.wikipedia.org/wiki/The_Good_Place).
