- Can now refine random generators.

1 files changed, 13 insertions, 0 deletions

diff --git a/stdlib/source/lux/math/random.lux b/stdlib/source/lux/math/random.lux
index b8db79ccb..28751e125 100644
--- a/stdlib/source/lux/math/random.lux
+++ b/stdlib/source/lux/math/random.lux
@@ -20,6 +20,7 @@
                    [stack #+ Stack]
                    [row #+ Row]
                    (tree [finger #+ Tree])))
+       (type [refinement #+ Refiner Refined])
        ))
 
 (type: #export #rec PRNG
@@ -66,6 +67,18 @@
       (wrap sample)
       (filter pred gen))))
 
+(def: #export (refine refiner gen)
+  {#.doc "Retries the generator until the output can be refined."}
+  (All [t r] (-> (Refiner t r) (Random t) (Random (Refined t r))))
+  (do Monad<Random>
+    [sample gen]
+    (case (refiner sample)
+      (#.Some refined)
+      (wrap refined)
+
+      #.None
+      (refine refiner gen))))
+
 (def: #export bool
   (Random Bool)
   (function (_ prng)