Gerbil is a new dialect of Scheme, designed around a multiresolution macro system.
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 plt's modules is that Gerbil modules are single instantiation, supporting high performance ahead of time compilation and compiled macros.
Gerbil has been my private Scheme for many years, evolved out of a set of common macros that i used across different implementations. As such i have multiple backends that work with the Gerbil macro system, but I have elected to base the primary 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.
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) 2007-2016 Dimitris Vyzovitis <vyzo -at- hackzen.org>
Gerbil is Free Software, distributed under the GNU LGPLv2.1 or later
and the Apache 2.0 license.
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
I have tested the bootstrap with Gambit v4.8.4, but older versions starting with v4.6.0 should work as well.
The only hard dependency is libcrypto from OpenSSL; important parts
of the standard library require it. All the other dependencies can be
configured at build-time by editing $GERBIL_HOME/src/std/build-config.ss.
The :std/xml library, which is built by default requires libxml2 to build;
edit build-config.ss and set the option (enabe libxml #f) if
you don't have libxml2 in your system.
After checking out the source code from Github, let $GERBIL_HOME be
the top directory of Gerbil.
Then:
$ cd $GERBIL_HOME/src
$ ./build.sh
this will execute a full bootstrap build in place, starting from the
pre-compiled Scheme sources in $GERBIL_HOME/src/bootstrap.
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)
There is some documentation at $GERBIL_HOME/doc, most notably
a introductory guide in markdown for seasoned Schemers.
You can read it rendered online at Github:
guide.md.
Beyond that, there is little further documentation at this point, because I haven't had the time to prepare some nice and coherent documentation that can help Scheme neophytes -- or people who like neat documentation before using a new Scheme system.
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.
The core language macros are defined in src/gerbil/prelude/core.ss.
This is the language that you get in the interpreter and what is available
when writing a new module without explicitly specifying a prelude.
Gerbil is under continuous use and development. The core language has been stable for a while, but I am busy porting batteries for the std library.
Patches (even for typos in the comments) are always welcome. No copyright assignment ever, you keep what you contribute.