Merge pull request #49 from coq-ext-lib/string-fold-direction

Fixing the fold direction for string to be consistent with list

Author: gmalecha

theories/Data/String.v

@@ -123,12 +123,12 @@ repeat constructor.
 Defined.
 
 Global Instance Foldable_string : Foldable string ascii :=
-  fun _ f =>
-    fix go acc ls :=
+  fun _ f base =>
+    fix go ls :=
     match ls with
-      | EmptyString => acc
-      | String l ls =>
-        go (f l acc) ls
+    | EmptyString => base
+    | String l ls =>
+      f l (go ls)
     end.
 
 Section string.