hslua – Lua interpreter interface for Haskell
Hslua provides bindings, wrappers, types, and helper functions to bridge haskell and lua.
The following cabal build flags are supported:
system-lua: Use the locally installed Lua version instead of the version shipped as part of HsLua.
pkg-configto discover library and include paths. This is used only when the
system-luaflag is set or implied.
lua501: Build against Lua 5.1; this implies the flag
lua502: Build against Lua 5.2; this implies the flag
luajit: Build against LuaJIT; this implies the flag
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
--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
Where are the coroutine related functions? Yielding from a coroutine works
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
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.
Increase user-friendlyness of error messages: The error message returned by
toHaskellFunctionhinted at the fact that the failing function is a Haskell function. This is mostly unnecessary information and might have confused users.
- Added cabal flag to allow fully safe garbage collection: Lua garbage
collection can occur in most of the API functions, even in those usually not
calling back into haskell and hence marked as optimizable. The effect of this
is that finalizers which call Haskell functions will cause the program to
hang. A new flag
allow-unsafe-gcis introduced and enabled by default. Disabling this flag will mark more C API functions as potentially calling back into Haskell. This has a serious performance impact.
ToLuaStackinstances for lazy ByteStrings are added.
- None-string error messages are handled properly: Lua allows error messages to be of any type, but the haskell error handlers expected string values. Tables, booleans, and other non-string values are now handled as well and converted to strings.
- Use newtype definitions instead of type aliases for LuaNumber and LuaInteger. This makes it easier to ensure the correct numeric instances in situations where Lua might have been compiled with 32-bit numbers.
- Instances of
Intare removed. The correctness of these instances cannot be guaranteed if Lua was compiled with a non-standard integer type.
- The flag
lua_32bitswas added to allow users to compile Lua for 32-bit systems.
- When reading a list, throw an error if the lua value isn't a table instead of silently returning an empty list.
- Tuples from pairs to octuples have been made instances of
- New functions
dofileare provided to load and run strings and files in a single step.
LuaStatuswas renamed to
Status, the Lua prefix was removed from its type constructors.
- The constructor
ErrFilewas added to
Status. It is returned by
loadfileif the file cannot be read.
- Remove unused FFI bindings and unused types, including all functions unsafe to use from within Haskell and the library functions added with 0.5.0. Users with special requirements should define their own wrappers and raw bindings.
- The module Foreign.Lua.Api.SafeBindings was merge into Foreign.Lua.Api.RawBindings.
- FFI bindings are changed to use newtypes where sensible, most notably
NumResults, but also the newly introduced newtypes
- Add functions
tonumberxwhich can be used to get and check values from the stack in a single step.
- The signature of
concatwas changed from
Int -> Lua ()to
NumArgs -> Lua ().
- The signature of
loadfilewas changed from
String -> Lua Intto
String -> Lua Status.
- The type
LTYPEwas renamed to
Type, its constructors were renamed to follow the pattern
LuaRelationwas renamed to
RelationalOperator, the Lua prefix was removed from its constructors.
- Add function
tolistto allow getting a generic list from the stack without having to worry about the overlapping instance with
- Supported Lua Versions now include Lua 5.2 and Lua 5.3. LuaJIT and Lua 5.1 remain supported as well.
use-pkgconfigwas added to allow discovery of library and include paths via pkg-config. Setting a specific Lua version flag now implies
system-lua. (Sean Proctor)
- The module was renamed from
Foreign.Lua. The code is now split over multiple sub-modules. Files processed with hsc2hs are restricted to Foreign.Lua.Api.
Luamonad (reader monad over LuaState) is introduced. Functions which took a LuaState as their first argument are changed into monadic functions within that monad.
- Error handling has been redesigned completely. A new LuaException was
introduced and is thrown in unexpected situations. Errors in lua which are
leading to a
longjmpare now caught with the help of additional C wrapper functions. Those no longer lead to uncontrolled program termination but are converted into a LuaException.
peekno longer returns
Maybe abut just
a. A LuaException is thrown if an error occurs (i.e. in situtations where Nothing would have been returned previously).
StackValuetypeclass has been split into
ToLuaStack. Instances not satisfying the law
x == push x *> peek (-1)have been dropped.
- Documentation of API functions was improved. Most docstrings have been copied from the official Lua manual, enriched with proper markup and links, and changed to properly describe hslua specifics when necessary.
- Example programs have been moved to a separate repository.
- Unused files were removed. (Sean Proctor)
- New raw functions for
luaopen_debugand their high-level wrappers (with names
- Remove custom versions of
- Drop support for GHC versions < 7.8, avoid compiler warnings.
- Ensure no symbols are stripped when linking the bundled lua interpreter.
tostringfunction definition. (Sean Proctor)
- Explicitly deprecate
strlen. (Sean Proctor)
- Add links to lua documentation for functions wrapping the official lua C API. (Sean Proctor).
tolistwasn't popping elements of the list from stack.
StackValue [Char]instance is removed,
StackValue ByteStringis added.
StackValue a => StackValue [a]instance is added. It pushes a Lua array to the stack.
tolistfunctions are added.
- Type errors in Haskell functions now propagated differently. See the
Scripting.Luadocumentation for detailed explanation. This should fix segfaults reported several times.
lua_errorfunction is removed, it's never safe to call in Haskell.
Related issues and pull requests: #12, #26, #24, #23, #18.
- Pkgconf-based setup removed. Cabal is now using
extra-librariesto link with Lua.
luajitflag is added to link hslua with LuaJIT.
Small bugfix related with GHCi running under Windows.
registerrawhsfunctionfunctions are added.
apicheckflag is added to Cabal package to enable Lua API checking. (useful for debugging)
luaL_unreffunctions are added.