hslua – Lua interpreter interface for Haskell

Hslua provides bindings, wrappers, types, and helper functions to bridge haskell and lua.

Build flags

The following cabal build flags are supported:

• system-lua: Use the locally installed Lua version instead of the version shipped as part of HsLua.

• use-pkgconfig: Use pkg-config to discover library and include paths. This is used only when the system-lua flag is set or implied.

• lua501: Build against Lua 5.1; this implies the flag system-lua as well.

• lua502: Build against Lua 5.2; this implies the flag system-lua as well.

• luajit: Build against LuaJIT; this implies the flag system-lua as well.

• allow-unsafe-gc: Allow optimizations which make Lua's garbage collection potentially unsafe; haskell finalizers must be handled with extreme care. This is enabled per default, as this is rarely a problem in practice.

• apicheck: Compile Lua with its API checks enabled.

• lua_32bits: Compile Lua for a 32-bits system (e.g., i386, PowerPC G4).

Example: using a different lua version

To use a system-wide installed Lua/LuaJIT when linking hslua as a dependency, build/install your package using --constraint="hslua +system-lua" or for LuaJIT: --constraint="hslua +luajit". For example, you can install Pandoc with hslua that uses system-wide LuaJIT like this:

cabal install pandoc --constraint="hslua +system-lua +luajit"

or with stack:

stack install pandoc --flag=hslua:luajit

FAQ

Where are the coroutine related functions? Yielding from a coroutine works via longjmp, which plays very badly with Haskell's RTS. Tests to get coroutines working with HsLua were unsuccessful. No coroutine related functions are exported from the default module for that reason. However, raw bindings to the C API functions are still provided in Foreign.Lua.RawBindings. If you get coroutines to work, or just believe that there should be wrapper functions for other reasons, we'd love to hear from you.

Why are there no predefined stack instances for default numerical types? HsLua defines instances for the FromLuaStack and ToLuaStack type-classes only if the following law holds: return x == push x *> peek x. Lua can be compiled with customized number types, making it impossible to verify the correctness of the above equation. Furthermore, instances for numerical types can be based on those of LuaInteger and LuaNumber and are easy to write. Therefor hslua doesn't provide any such instances.