don't hold onto generators

1 files changed, 9 insertions, 6 deletions

diff --git a/src/PPL/Internal.hs b/src/PPL/Internal.hs
index de48a3f..b7d49ee 100644
--- a/src/PPL/Internal.hs
+++ b/src/PPL/Internal.hs
@@ -45,12 +45,15 @@ mutateTree :: RandomGen g => Double -> Double -> g -> Tree -> Tree
 mutateTree p q g (Tree a ts) =
   let (r, g1) = random g
       (b, g2) = random g1
-   in if r >= p
-        then Tree a (mutateTrees p q g1 ts)
-        else
-          if r < p * q
-            then Tree (1 - a) (mutateTrees p q g1 ts)
-            else Tree b (mutateTrees p q g2 ts)
+   in Tree
+        ( if r >= p
+            then a
+            else
+              if r < p * q
+                then 1 - a
+                else b
+        )
+        (mutateTrees p q g2 ts)
   where
     mutateTrees p q g (t : ts) =
       let (g1, g2) = R.split g