Michael Snoyman wrote:
Note that I wasn't necessarily advocating such a pragma. And a lot of my XML code actually *does* use two IsString instances at the same time, e.g.:
Element ("img" :: Name) (singleton ("href" :: Name) ("foo.png" :: Text)) [NodeComment ("No content inside an image" :: Text)]
In this particular case, would it make sense to use smart constructors instead? The idea is that you can put the polymorphism in two places: either make the "output" polymorphic, or make the "input" polymorphic. The latter would correspond to a type element :: (IsString name, IsString s, IsMap map) => name -> map name s -> [Element] element name map = Element (toName name) (toMap map) One benefit would be that the function will accept any list as a map, not just list literals. Best regards, Heinrich Apfelmus -- http://apfelmus.nfshost.com