Gerbil Scheme

Gerbil is an opinionated dialect of Scheme with a state of the art macro and module system on the Gambit runtime.

The macro system is based on quote-syntax, and provides the full meta-syntactic tower with a native implementation of syntax-case. It also provides a full-blown module system, similar to PLT Scheme's (sorry, Racket) modules. The main difference from Racket is that Gerbil modules are single instantiation, supporting high performance ahead of time compilation and compiled macros.

• License and Copyright
• Installation
• Using Gerbil
• Documentation
• Epilogue

License and Copyright

The source code is distributed with the Gambit license; that means that Gerbil on Gambit is dual licensed under LGPLv2.1 and Apache 2.0.

Gerbil's primary author and maintainer is vyzo-at-hackzen.org, aka in the Net as Dimitris Vyzovitis. The obligatory copyright notice, had I bothered polluted everything with more than a (C) vyzo at hackzen.org, would read like this:

(C) 2007-2017 Dimitris Vyzovitis <vyzo -at- hackzen.org>
Gerbil is Free Software, distributed under the GNU LGPLv2.1 or later
and the Apache 2.0 license.

Installation

Source Code

The source code for Gerbil is hosted on Github. You can obtain the source tree directly in the command line by cloning the repository:

$ git clone https://github.com/vyzo/gerbil.git

Dependencies

I have tested the bootstrap with Gambit v4.8.x, but older versions starting with v4.6.0 used to work as well.

The core system has no dependencies outside Gambit, but the standard library has several mostly optional dependencies. The only hard dependency is libcrypto from OpenSSL; important parts of the standard library require it. You may need to install openssl-dev in ubuntu and similar systems.

All the other dependencies are soft; library modules with foreign dependencies are not built by default, with the exception of zlib. The optional libraries can be enabled at build-time by editing $GERBIL_HOME/src/std/build-config.ss. You can also enable features later, by editing build-config.ss and running build.ss in $GERBIL_HOME/src/std

Build Instructions

After checking out the source code from Github, let $GERBIL_HOME be the top directory of Gerbil. Then:

$ cd $GERBIL_HOME/src
$ ./build.sh

Using Gerbil

The Gerbil interpreter is $GERBIL_HOME/bin/gxi, and the compiler is $GERBIL_HOME/bin/gxc.

If you want an interactive Gerbil shell just execute the interpreter directly by running gxi.

If you want to write an executable Gerbil script, add $GERBIL_HOME/bin to your PATH and use the following for your magic:

#!/usr/bin/env gxi-script

You can define a main procedure in your script that will receive the command line arguments.

For an example script, put the following in hello.ss

#!/usr/bin/env gxi-script

(def (main . args)
 (displayln "Hello world! My arguments are " args))

Running the script with

chmod +x hello.ss
./hello.ss 1 2 3

should produce the following output:

Hello world! My arguments are (1 2 3)

Documentation

The documentation is a work in progress, but there are some resources that should get you started:

• The Introduction to Gerbil, an introductory guide for seasoned Schemers.
• The Gerbil wiki at Github contains a small but growing collection of pages that can help you get started with Gerbil.
• The Gerbil Core Prelude documents the core language prelude.
• The Gerbil Tutorial, which is still in its infancy.

Probably the best way to dive into gerbil is by reading the sources, as all the main language features are exercised in one way or another within the implementation.

Depending on your inclinations, there are several starting points:

• If you are interested in Gerbil macrology, then the place to start is the core prelude. This is the language that you get in the interpreter and what is available when writing a new module without explicitly specifying a prelude.
• If you are interested in the Gerbil expander internals, then you should look at the expander sources.
• If you are interested in the Gerbil compiler internals, then you should look at the compiler sources.
• If you are interested in general purpose programming, then you should look at the stdlib sources.

For questions and support, you can come say hi in #gerbil-scheme on irc at freenode.net.

Epilogue

Gerbil has been my private Scheme for many years, evolved out of a set of common macros that i used across different implementations and eventually a full-blown PLT macro language. As such I have had multiple backends that work with the Gerbil macro system, but I have elected to base the canonical version of Gerbil on Gambit.

At the prompting of some friends (they know who they are), who had seen private versions of Gerbil, I decided to release it in public with a clean bootstrap version that bootstraps on gambit with a precompiled version of the macro system and compiler. That means that the system is entirely self-hosted in Gambit.

Gerbil is under continuous use and development. The core language has been stable for a while, but I am busy porting batteries, adding features, fixing bugs, and expanding the scope of syntactic abstraction.

Patches (even for typos in the comments) are always welcome. No copyright assignment ever, you keep what you contribute.