[make sectionType O(1)
Helmut Grohne <grohne@cs.uni-bonn.de>**20150331124443
 Ignore-this: f9a718a1cf4caa2a69a99b61b0963ef2
 
 Previously it would be O(number of arrows) and since it can be called a lot,
 this can become a bottleneck.
] hunk ./src/Syntax/Type.hs 115
+sectionType (AppT (AppT a e1) e2) | a == arrowCon = e2
+sectionType (ForallT cxt t) = quantify (sectionType t) cxt
+sectionType t = error $ "Types.sectionType: no function type " ++ show t
hunk ./src/Syntax/Type.hs 119
-sectionType  t =
-    case tail . unArrowT $ t of 
-        [] -> error $ "Types.sectionType: no function type " ++ (show t)
-        tl -> arrowT tl
-        