+
+-- HAllable
+class HAllable f l where
+ type HAll f l
+ hAll :: f -> l -> HAll f l
+
+instance HAllable f HNil where
+ type HAll f HNil = True
+ hAll _ _ = undefined :: True
+
+instance ( IfT (Apply f x) (HAll f xs) False
+ , Applyable f x
+ , HAllable f xs
+ ) => HAllable f (HCons x xs) where
+ type HAll f (HCons x xs) = If (Apply f x)
+ (HAll f xs)
+ False
+ hAll f (HCons x xs) = ifT (apply f x)
+ (hAll f xs)
+ (undefined :: False)
+
+-- HLength
+type family HLength l
+type instance HLength HNil = D0
+type instance HLength (HCons e l) = Succ (HLength l)