Add FieldHKD

obsidiansystems · Jan 16, 2022 · c2bbc0b · c2bbc0b
1 parent 4b86459
commit c2bbc0b
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diff --git a/lib/tabulation/CHANGELOG.md b/lib/tabulation/CHANGELOG.md
@@ -1,5 +1,7 @@
 # Revision history for tabulation
 
+* Add FieldHKD - a wrapper to allow mixing/reusing a non-HDK associated GADT with the higher kinded data record
+
 ## 0.1.0.0 -- 2019-05-24
 
 * First version. Basically carve out this library as a place for the HasFields class.
diff --git a/lib/tabulation/src/Data/Tabulation.hs b/lib/tabulation/src/Data/Tabulation.hs
@@ -1,5 +1,6 @@
-{-# LANGUAGE TypeFamilies #-}
+{-# LANGUAGE GADTs #-}
 {-# LANGUAGE RankNTypes #-}
+{-# LANGUAGE TypeFamilies #-}
 
 module Data.Tabulation where
 
@@ -18,4 +19,8 @@ class HasFields a where
   traverseWithField t r = tabulateFieldsA (\f -> t f (indexField r f))
   indexField :: a -> Field a x -> x
   indexField a f = a ^. fieldLens f
-  {-# MINIMAL fieldLens, tabulateFieldsA #-}
+  {-# MINIMAL fieldLens, tabulateFieldsA #-}
+
+-- | A wrapper to allow mixing/reusing a non-HDK associated GADT with the higher kinded data record
+data FieldHKD field f x where
+  FieldHKD :: field x -> FieldHKD field f (f x)