Added function elemIndex to SCL Prelude

[simantics/platform.git] / bundles / org.simantics.scl.runtime / scl / Prelude.scl

diff --git a/bundles/org.simantics.scl.runtime/scl/Prelude.scl b/bundles/org.simantics.scl.runtime/scl/Prelude.scl
index f06acb29fce55e74e98c111364ede07908947df9..c04cc8625aa0be2bceb1ab372f8f9fe5a7eca5c4 100644 (file)
--- a/bundles/org.simantics.scl.runtime/scl/Prelude.scl
+++ b/bundles/org.simantics.scl.runtime/scl/Prelude.scl
@@ -1081,12 +1081,12 @@ replicate n v = build (\empty cons ->
 
 /// FunctorM ///
 
-class (Functor f) => FunctorM f where
+class (FunctorE f) => FunctorM f where
     "`mapM f` is equivalent to `sequence . map f`."
-    mapM :: Monad m => (a -> m b) -> f a -> m (f b)
+    mapM :: Monad m => (a -> <e> m b) -> f a -> <e> m (f b)
     "Evaluate each action in the sequence from left to right, and collect the results."
     sequence :: Monad m => f (m a) -> m (f a) 
-    mapM f l = sequence (fmap f l)
+    mapM f l = sequence (map f l)
 
 /// MonadE ///
 
@@ -1162,6 +1162,14 @@ class IndexedSequence f where
     "`seq ! i` returns the `i`th element of the sequence `seq`. Indexing starts from zero."
     (!) :: f a -> Integer -> a
 
+"Returns the first element of a sequence"
+@inline
+first l = l!0
+
+"Returns the last element of a sequence"
+@inline
+last l = l!(length l-1)
+
 instance IndexedSequence [] where
     (!) = getList
 
@@ -1941,7 +1949,7 @@ importJava "org.simantics.scl.runtime.Lists" where
     Given a list of values and a function computing a key for each value, the function produces a function that finds a value
     effeciently for the given key.
     """
-    indexBy ::  (a -> b) -> [a] -> b -> Maybe a
+    indexBy ::  (a -> <e> b) -> [a] -> <e> (b -> Maybe a)
     
     "Works like `index` but uses the given functions as hash codes and equality."
     indexWith :: (a -> Integer) -> (a -> a -> Boolean) -> [(a,b)] -> a -> Maybe b
@@ -1995,6 +2003,16 @@ elemMaybe el m = match m with
     Just el2 -> el == el2
     Nothing -> False
 
+"`elemIndex el lst` returns the index of the first element in the given list `lst` which is equal (by ==) to the query element, or Nothing if there is no such element."
+elemIndex :: a -> [a] -> Maybe Integer
+elemIndex el l = loop 0
+  where
+    len = length l
+    loop i | i < len = if el == l!i
+                       then Just i
+                       else loop (i+1)
+           | otherwise = Nothing
+
 """
 Computes a list that contains only elements that belongs to both input lists.
 """