Make it compile with MicroHs

.github/workflows/ci.yaml

@@ -10,13 +10,14 @@ on:
 
 jobs:
   build:
+    name: ghc-${{ matrix.ghc }}
     runs-on: ubuntu-latest
     strategy:
       fail-fast: false
       matrix:
         ghc: ['8.0', '8.2', '8.4', '8.6', '8.8', '8.10', '9.0', '9.2', '9.4', '9.6', '9.8', '9.10', '9.12']
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v5
       - uses: haskell-actions/setup@v2
         id: setup-haskell
         with:
@@ -29,3 +30,24 @@ jobs:
           key: ${{ runner.os }}-${{ matrix.ghc }}
       - name: Build
         run: cabal build
+
+  mhs:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v5
+        with:
+          path: parallel
+      - name: Checkout MicroHs repository
+        uses: actions/checkout@v5
+        with:
+          repository: augustss/MicroHs
+          path: mhs
+      - name: Install MicroHs
+        run: |
+          cd mhs
+          make minstall
+          echo "$HOME/.mcabal/bin" >> $GITHUB_PATH
+      - name: Build
+        run: |
+          cd parallel
+          mcabal -r build

Control/Parallel.hs

@@ -28,9 +28,9 @@ module Control.Parallel (
 
 #ifdef __GLASGOW_HASKELL__
 import qualified GHC.Conc (par, pseq)
+#endif
 
 infixr 0 `par`, `pseq`
-#endif
 
 -- Maybe parIO and the like could be added here later.
 
@@ -54,7 +54,7 @@ par :: a -> b -> b
 #ifdef __GLASGOW_HASKELL__
 par = GHC.Conc.par
 #else
--- For now, Hugs does not support par properly.
+-- For now, Hugs and MicroHs don't support par properly.
 par a b = b
 #endif
 

Control/Parallel/Strategies.hs

@@ -146,15 +146,17 @@ module Control.Parallel.Strategies (
     NFData
   ) where
 
-#if !MIN_VERSION_base(4,8,0)
+#if defined(__MHS__) || !MIN_VERSION_base(4,8,0)
 import Data.Traversable
+#endif
+#if !MIN_VERSION_base(4,8,0)
 import Control.Applicative
 #endif
 import Control.Parallel
 import Control.DeepSeq (NFData(rnf))
 import Control.Monad.Fix (MonadFix (..))
 
-#if MIN_VERSION_base(4,4,0)
+#if defined(__GLASGOW_HASKELL__) && MIN_VERSION_base(4,4,0)
 import System.IO.Unsafe (unsafeDupablePerformIO)
 import Control.Exception (evaluate)
 #else
@@ -164,8 +166,10 @@ import Control.Monad
 
 import qualified Control.Seq
 
+#ifdef __GLASGOW_HASKELL__
 import GHC.Exts
 import GHC.IO (IO (..))
+#endif
 
 infixr 9 `dot`     -- same as (.)
 infixl 0 `using`   -- lowest precedence and associate to the left
@@ -280,7 +284,11 @@ instance Applicative Eval where
 
 instance Monad Eval where
   return = pure
+#  ifdef __GLASGOW_HASKELL__
   Done x >>= k = lazy (k x)   -- Note: pattern 'Done x' makes '>>=' strict
+#  else
+  Done x >>= k = k x
+#  endif
 
 instance MonadFix Eval where
   mfix f = let r = f (runEval r) in r
@@ -463,10 +471,14 @@ rdeepseq x = do rseq (rnf x); return x
 
 -- | 'rpar' sparks its argument (for evaluation in parallel).
 rpar :: Strategy a
+#ifdef __GLASGOW_HASKELL__
 #if __GLASGOW_HASKELL__ >= 702
-rpar  x = Eval $ IO $ \s -> spark# x s
+rpar x = Eval $ IO $ \s -> spark# x s
+#else
+rpar x = case (par# x) of _ -> Done x
+#endif
 #else
-rpar  x = case (par# x) of { _ -> Done x }
+rpar x = case par x () of () -> Done x
 #endif
 {-# INLINE rpar  #-}
 

Control/Seq.hs

@@ -59,7 +59,7 @@ module Control.Seq
        ) where
 
 import Control.DeepSeq (NFData, deepseq)
-#if MIN_VERSION_base(4,8,0)
+#if defined(__GLASGOW_HASKELL__) && MIN_VERSION_base(4,8,0)
 import Data.Foldable (toList)
 #else
 import Data.Foldable (Foldable, toList)

parallel.cabal

@@ -25,6 +25,7 @@ tested-with:
   GHC == 8.4.4
   GHC == 8.2.2
   GHC == 8.0.2
+  MHS
 
 description:
     This package provides a library for parallel programming.
@@ -68,6 +69,3 @@ library
     if impl(ghc >= 6.11)
         -- To improve parallel performance:
         ghc-options: -feager-blackholing
-
-    if impl(ghc >= 7.2.1)
-        build-depends: ghc-prim