From: "Rene de Visser" test9 = [d| add_rel1 value = $(exp) value |] where exp = [| (\value -> modify (\db -> $(updater) db (Set.insert value (rel1 db)))) |] where updater = [|(\db value -> db{rel1 = value}) |] --updater = LamE [VarP db_2,VarP value_3] (RecUpdE (VarE db_2) [(DataBase.rel1,VarE value_3)]) where db_2 = mkName "db_2" ; value_3 = mkName "value_3"

Ok, I've found the error, that needs to be updater = lamE [varP db_2,varP value_3] (recUpdE (varE db_2) [fieldExp 'DataBase.rel1 (varE value_3)]) Rene.