priv/stdlib/List.aes

@@ -102,10 +102,8 @@ namespace List =
     []   => reverse(acc)
     h::t => map_(f, t, f(h)::acc)
 
-  function flat_map(f : 'a => list('b), l : list('a)) : list('b) = flat_map_(f, l, [])
+  function flat_map(f : 'a => list('b), l : list('a)) : list('b) =
-  private function flat_map_(f : 'a => list('b), l : list('a), acc : list('b)) : list('b) = switch(l)
+    ListInternal.flat_map(f, l)
-    []   => reverse(acc)
-    h::t => flat_map_(f, t, reverse(f(h)) ++ acc)
 
   function filter(p : 'a => bool, l : list('a)) : list('a) = filter_(p, l, [])
   private function filter_(p : 'a => bool, l : list('a), acc : list('a)) : list('a) = switch(l)

priv/stdlib/ListInternal.aes

@@ -1,9 +1,9 @@
 namespace ListInternal =
 
-  private function reverse_(xs : list('a), ys : list('a)) : list('a) =
+  // -- Flatmap ----------------------------------------------------------------
+
+  function flat_map(f : 'a => list('b), xs : list('a)) : list('b) =
     switch(xs)
-      []      => ys
+      []      => []
-      x :: xs => reverse_(xs, x :: ys)
+      x :: xs => f(x) ++ flat_map(f, xs)
-
-  function reverse(xs : list('a)) = reverse_(xs, [])