Haskell & MRuby

[synth-me]

How May i embed mruby in Haskell ? I can imagine using some FFI but hasn't been working as i tried the traditional mathods for it. Somebody have any ideia about how can I do it ?

[dearblue]

I was able to run Ruby code from Haskell through mruby.
This is my first time programming Haskell, so I'm probably making a lot of mistakes.
The compiler I used this time was ghc.

(1) Get the mruby source code and build libmruby.a

% git clone https://github.com/mruby/mruby.git
% cd mruby
% rake

Try bin/mruby-config on the same directory if checking the linker flag.

% bin/mruby-config --ldflags
-L/var/tmp/mruby/build/host/lib
% bin/mruby-config --libs
-lmruby -lm

(2) Edit Haskell code (file name is mruby-ffi.hs)

{-# LANGUAGE ForeignFunctionInterface #-}

module Main where

import Foreign.C.String
import Foreign.C.Types
--import Foreign.Marshal.Alloc -- for free
import Foreign.Ptr

data MRubyState
newtype MRubyValue = Storable CUIntPtr

-- from mruby.h
foreign import ccall "mrb_open" mrb_open :: IO (Ptr MRubyState)
foreign import ccall "mrb_close" mrb_close :: Ptr MRubyState -> IO ()
foreign import ccall "mrb_p" mrb_p :: Ptr MRubyState -> MRubyValue -> IO ()

-- from mruby/compile.h
foreign import ccall "mrb_load_string" mrb_load_string :: Ptr MRubyState -> CString -> IO (MRubyValue)

main :: IO ()
main = do
  let rubycode = "puts \"Hello world!!!\"; \"from #{MRUBY_DESCRIPTION}\""
  mrb <- mrb_open
  --cstr <- newCString rubycode
  --val <- mrb_load_string mrb cstr
  --free cstr
  val <- withCString rubycode (\ cstr -> mrb_load_string mrb cstr)
  mrb_p mrb val
  mrb_close mrb

{-
 - References:
 - - (ja) https://yunomu.hatenablog.jp/entry/2012/07/31/005513
 - - (ja) https://xtech.nikkei.com/it/article/COLUMN/20080805/312151/
 - - (ja) https://qiita.com/arowM/items/9ebfb7cafecd99290663
 - - (en) https://wiki.haskell.org/Foreign_Function_Interface
 - - (en) https://hackage.haskell.org/package/base-4.16.0.0/docs/Foreign-C-String.html
 -}

(3) Compiling and running Haskell code

% ghc `bin/mruby-config --ldflags --libs` mruby-ffi.hs
% ./mruby-ffi
Hello world!!!
"from mruby 3.0.0 (2021-03-05)"

[synth-me]

I'll have a look at it and then i'll get you a review of that code. Although , look like that this solution is very close to what i've been trying but more detailed. I hope it works !

[synth-me]

Just to say , this solution worked but only on linux distributions i tried windows 10 and it didn't work although it's great to me

[rubyFeedback]

It may be useful to state why it did not work. Perhaps matz can get some ideas what to improve in mruby to make it work better on win10/11. I use linux myself but an elderly relative depends on win10 so ruby and mruby working on windows is useful.