From: Hannu Niemistö <hannu.niemisto@semantum.fi>
Date: Mon, 25 Sep 2017 09:41:03 +0000 (+0300)
Subject: Added MMap.getOrCreate
X-Git-Tag: v1.31.0~171
X-Git-Url: https://gerrit.simantics.org/r/gitweb?a=commitdiff_plain;h=refs%2Fchanges%2F18%2F1018%2F1;p=simantics%2Fplatform.git

Added MMap.getOrCreate

refs #7503

Change-Id: Ibc03b5c51365e4d5c2d2250fbf7265adc298a84a
---

diff --git a/bundles/org.simantics.scl.runtime/scl/MMap.scl b/bundles/org.simantics.scl.runtime/scl/MMap.scl
index 18e5866c0..085728c58 100644
--- a/bundles/org.simantics.scl.runtime/scl/MMap.scl
+++ b/bundles/org.simantics.scl.runtime/scl/MMap.scl
@@ -35,6 +35,15 @@ importJava "java.util.Map" where
     remove :: T a b -> a -> <Proc> (Maybe b)
     clear :: T a b -> <Proc> ()
 
+@inline
+getOrCreate :: T a b -> (a -> <e> b) ->  a -> <Proc,e> b
+getOrCreate m f k = match get m k with
+    Just v -> v
+    Nothing -> do
+        v = f k
+        put m k v
+        v  
+
 @inline
 iter :: (a -> b -> <e> ()) -> T a b -> <e,Proc> ()
 iter f m = MSet.iter (\entry -> f (keyOf entry) (valueOf entry)) (entrySet m)