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Scheme2Luac

made at Recurse Center

Overview

A Scheme compiler for the Lua VM, still in progress. It is designed for Lua 5.1 (download here). Build using Haskell's package manager stack (available here):

$ git clone https://github.com/adamrk/scheme2luac.git
$ cd scheme2luac
$ stack build

To compile a Scheme script and run in Lua, first check you have Lua 5.1:

$ lua -v

This should return 'Lua 5.1.* Copyright (C) 1994-2012 Lua.org, PUR-Rio' or similar.

Then create scheme script (test.scm in this example) and run:

$ stack exec -- scheme2luac-exe test.scm out.luac
$ lua out.luac

Implemented Components of R5RS Standard

This project aims to implement the R5RS scheme standard. These expressions have been implemented:

  • let
  • define
  • lambda
  • if
  • quote
  • eval

as well as several primitive functions (see the list of primitives in CodeGenerator.hs). There is also support for macros using define-syntax.

Differences from R5RS Standard

  • The full heirarchy of numerical types is not supported. All numbers are converted to Lua Numbers which are doubles.
  • quasiquote is not supported.
  • quoted symbols do not yet print properly.
  • equivalence predicates are not supported.
  • input/output ports are not yet supported
  • many derived expressions are not supported, but can easily be implemented since we have support for macros.

Using 'eval'

If your scheme script uses the eval function then it will need to have access to the compiler at runtime. This requires a special compilation process (these commands are in the file build.sh):

$ stack build
$ stack exec -- ghc LibCompiler.hs -shared -dynamic -fPIC -o libcompiler.so -lHSrts-ghc8.0.2
$ stack exec -- ghc libcompilerhelper.c -no-hs-main -optl -L. -lcompiler -o lualibhelper.so -shared -fPIC -dynamic

Note that you will need to change the option -lHSrts-ghc8.0.2 to match with your version of GHC. Check which version of ghc you're running with stack exec -- ghc --version. You will also need the lua header files lua.h and luaconf.h which are available here. Modify the -L. flag to the path to these header files.

This will create two shared libraries: libcompiler.so and lualibhelper.so. At runtime Lua must be able to access the lualibhelper.so library and the path to libcompiler.so must be in the LD_LIBRARY_PATH environment variable. Otherwise you will see an error like this:

lua: error loading module 'lualibhelper' from file './lualibhelper.so':
    libcompiler.so: cannot open shared object file: No such file or directory