= Millilisp - a tiny Lisp compiler

Millilisp (or simply mlisp) is an attempt to create a compiler for a small subset of Common Lisp. It covers a very narrow range of the language's features and it's nothing but a toy, actually.

== Dependencies

• Ruby, http://www.ruby-lang.org
• Nasm, http://www.nasm.us
• A C compiler

Millilisp has been developed on a 32 bit GNU/Linux but it should be easy to port it to other operating systems.

== Installation

$ make && sudo make install

If you'd like to install it elsewhere set the +PREFIX+ variable:

$ export PREFIX=/usr && make && sudo make install

See the variables on top of the Makefile if you'd like to make some additional adjustments.

== Usage

Assuming that 'file.lisp' contains code written in a subset of Common Lisp supported by the compiler, running

$ mlispc file.lisp

will create an 'a.out' binary in the current directory. See mlisp --help to see all command line options.

If 'libmlisp.a' has been installed in a non-standard directory your C compiler has to be pointed to it using the +LDFLAGS+ variable, for example

$ LDFLAGS='-L /opt/mlisp/lib' mlispc file.lisp

You can choose the C compiler you'd like mlispc to use by defining the +CC+ environment variable.

== How does it work

The compiler -- including a lexer and a parser -- is written in Ruby. It builds trees of sexps represented by instances of subclasses of Nodes::Node. Intermediate trees are analysed and modified by handlers of special types of nodes -- defuns, conds, quotes and lambdas -- and finally checked for semantic correctness. The result is sent to an emitter which outputs x86 assembly. The code is fed to nasm, which creates an object file. The output is linked with 'libmlisp.a' and saved as an executable.

The standard library, 'libmlisp.a', is implemented in ANSI C and Lisp. The most basic functionality is defined in 'stdlib.c'. Other functions, which are based on those written in C, can be found in 'funcs.lisp'. The part of the library implemented in Lisp is compiled by Millilisp.

Definitions of data structures used in binaries created by Millilisp can be found in 'stdlib.c'.

== Things to do

Millilisp is light years from being called a Common Lisp implementation. There are a lot of missing features, among which the highest priority has been assigned to:

• Floating point numbers
• Basic arithmetic and comparison functions
• String operations (probably using an external safe string library)
• Parsing comments
• Files IO support

Apart from the supported subset of Common Lisp there are other issues which need some work.

• A REPL
• Freeing memory or simply using Boehm's GC
• Tail call optimisation would be welcome as well

== Copyrights

(C) 2010 Jan Stępień

Millilisp is free software: you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public License along with this program. If not, see http://www.gnu.org/licenses/.