From 3517183bb2c4687d9360a19e89158d45d39308e0 Mon Sep 17 00:00:00 2001
From: Florent Becker <florent.becker@univ-orleans.fr>
Date: Mon, 24 Mar 2014 14:59:32 +0100
Subject: [PATCH] Make Diagrams.Transform.under more polymorphic

---
 src/Diagrams/Transform.hs | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/Diagrams/Transform.hs b/src/Diagrams/Transform.hs
index 91e9fbb6..b3c379d9 100644
--- a/src/Diagrams/Transform.hs
+++ b/src/Diagrams/Transform.hs
@@ -11,6 +11,8 @@
 --
 -----------------------------------------------------------------------------
 
+{-# LANGUAGE TypeFamilies #-}
+
 module Diagrams.Transform
     ( -- * Transformations
       Transformation, inv, transl, apply, papply
@@ -52,5 +54,5 @@ conjugate t1 t2  = inv t1 <> t2 <> t1
 --   @
 --
 --   for all transformations @t1@ and @t2@.
-under :: Transformable a => (a -> a) -> Transformation (V a) -> a -> a
+under :: (Transformable a, Transformable b, V a ~ V b) => (a -> b) -> Transformation (V a) -> a -> b
 f `under` t = transform (inv t) . f . transform t