History!

This is a Scheme implementation I wrote in late 2017 / early 2018. It's angling towards being an R7RS Scheme but falls pretty short of supporting a lot of the specification. It's pretty much on ice, but put here for posterity.

A couple of thoughts I thought were somewhat interesting:

• It's self hosting via a compiler to bytecode, but earlier stages of code are always written in a limited dialect supported by a simple C++ interpreter, so it's not difficult to port between architectures. (In fact while writing this README I compiled it on ARM64 OSX for the first time and it worked).

• It used a little reader hack to make implicit renaming macros the basis of writing macros. Putting return values into #` syntax (that in syntax-case is used for "quasisyntax") causes all values not put in #, to be wrapped in renames.

• Native compiler for x64 written with DynASM (from LuaJIT). This may have bitrotted, it's not been tested recently!

Original README

Arete is a low-footprint, high performance implementation of the Scheme programming language in C++ and itself.

Why?

Arete was written mostly for fun. I also made it as a platform for experimenting with more radical programming language design and implementation, but for the moment it's essentially a vanilla Scheme.

Features

• Compacting garbage collection
• Native compilation
• Hygienic macros and modules

Usage

Currently:

make heap.boot
bin/arete --save-image heap.boot

Will bootstrap the expander and compiler, then save them into a loadable image. Prepending heap.boot will make the files in examples/ and REPL work as expected, for example:

bin/arete heap.boot --repl

Will run the read-eval-print loop.

bin/arete heap.boot examples/life.scm 

Will run a simple Conway's Game of Life simulation.

make test-all

Will run all tests. Since Arete has not been tested on a wide variety of systems, doing this before attempting to use it is probably a good idea.

Dependencies

Arete uses the C++ STL, and optionally

• linenoise-ng from ArangoDB (for nice cross-platform REPL, included in the repository)
• DynASM (for native compilation, included in the repository)
• SDL2
• Python (for building & testing only)

R?RS/SRFI compliance.

Arete currently supports some features of R5RS and R7RS. Full compliance is not the primary goal at present, but I have tried to hew to the standards. If you miss something, open an issue :)

Noted issues

• equal? does not handle shared structure
• Continuations not supported
• eval does not support environment arguments