Darrin Thompson wrote:
I thought that I should be able to write something like the toHtml
function below with pure H98, but when I went to write it I ended up
needing fundeps. Is there a way to express this without using any
extensions?
The idea was to take a remotely Dom-like tree and flatten it into a
string, but not require any particular string type.
data (IsString s, Monoid s) => Dom s =
Element s [Attr s] [Dom s] |
Text s
data (IsString s, Monoid s) => Attr s = Attr s s
class (Monoid s, IsString s) => HTML d s | d -> s where
toHtml :: d -> s
instance (Monoid s, IsString s) => HTML (Dom s) s where
instance (Monoid s, IsString s) => HTML (Attr s) s where
The H98 way is to make a class for type constructors:
class HTML d where
toHTML :: (Monoid s, IsString s) => d s -> s
instance HTML Dom where ...
instance HTML Attr where ...
Btw, naming the class "HTML" is feels wrong, something like Serialize is
probably a better fit.
Regards,
apfelmus
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