X-Git-Url: https://gerrit.simantics.org/r/gitweb?p=simantics%2Fplatform.git;a=blobdiff_plain;f=bundles%2Forg.simantics.scl.runtime%2Fscl%2FPrelude.scl;h=f983251093272d2168cb9eacc05db4542660afa0;hp=03eabb66fb8ecd2ff7218fa5191db648350ee280;hb=9d780ffc68dbcb27bd90b5f80f4288de62d149fd;hpb=77e4291d372e7b4b40ee868ad61cc07c51de8c6b

diff --git a/bundles/org.simantics.scl.runtime/scl/Prelude.scl b/bundles/org.simantics.scl.runtime/scl/Prelude.scl
index 03eabb66f..f98325109 100644
--- a/bundles/org.simantics.scl.runtime/scl/Prelude.scl
+++ b/bundles/org.simantics.scl.runtime/scl/Prelude.scl
@@ -963,6 +963,9 @@ A class of monads with zero element satisfying
 """ 
 class (Monad m) => MonadZero m where
     mzero :: m a
+    mfilter :: (a -> Boolean) -> m a -> m a
+    
+    mfilter p m = m >>= (\x -> if p x then return x else mzero)
 
 "Injects a boolean test to a type beloning to `MonadZero`."
 guard :: MonadZero m => Boolean -> m ()
@@ -1093,6 +1096,7 @@ class (FunctorE f) => FunctorM f where
 /// MonadE ///
 
 class (FunctorE m, Monad m) => MonadE m where
+    "An effectful version of the bind operator `(>>=)`"
     bindE :: m a -> (a -> <e> m b) -> <e> m b
 
 instance MonadE Maybe where
@@ -1105,7 +1109,26 @@ instance MonadE (Either a) where
 
 instance MonadE [] where
     bindE l f = concatMap f l
+
+@inline
+"An effectful version of the Kleisli composition operator `(>=>)`"
+compE :: MonadE m => (a -> <e> m b) -> (b -> <f> m c) -> a -> <e,f> m c
+compE f g x = (f x) `bindE` g
+
+/// MZeroE ///
+
+class (MonadE m, MonadZero m) => MonadZeroE m where
+    filter :: (a -> <e> Boolean) -> m a -> <e> m a
+    
+    filter p m = m `bindE` (\x -> if p x then return x else mzero)   
     
+instance MonadZeroE [] where
+    filter = filterList
+    
+instance MonadZeroE Maybe where
+    filter p (Just x) | not (p x) = Nothing
+    filter _ m = m 
+
 /// Category ///
 
 "Identity function."
@@ -1292,6 +1315,7 @@ fromMaybe default maybeValue = match maybeValue with
     _ -> default
 
 "`maybe def f v` returns `def` if `v=Nothing` and `f x` if `v=Just x`."
+@inline
 maybe :: b -> (a -> <e> b) -> Maybe a -> <e> b
 maybe n _ Nothing  = n
 maybe _ f (Just x) = f x
@@ -1503,11 +1527,11 @@ snd :: (a,b) -> b
 snd (x,y) = y
 
 @inline
-mapFst :: (a -> b) -> (a,c) -> (b,c)
+mapFst :: (a -> <e> b) -> (a,c) -> <e> (b,c)
 mapFst f (x,y) = (f x, y)
 
 @inline
-mapSnd :: (a -> b) -> (c,a) -> (c,b)
+mapSnd :: (a -> <e> b) -> (c,a) -> <e> (c,b)
 mapSnd f (x,y) = (x, f y)
 
 instance (Ord a, Ord b) => Ord (a, b) where
@@ -1840,10 +1864,10 @@ foldr1 f l = loop (l!(len-1)) (len-2)
 `filter pred lst` returns those elements of `lst` that the predicate `pred` accepts. For example
 
     filter (> 3) [1, 2, 3, 4, 5, 6] = [4, 5, 6]
-""" 
+"""
 @inline
-filter :: (a -> <e> Boolean) -> [a] -> <e> [a]
-filter p l = build (\empty cons -> foldl (\cur x -> if p x then cons cur x else cur) empty l)
+filterList :: (a -> <e> Boolean) -> [a] -> <e> [a]
+filterList p l = build (\empty cons -> foldl (\cur x -> if p x then cons cur x else cur) empty l)
 
 """
 Takes those elements of the input list that match `(Just x)` and adds the contents to the resulting list. For example,