On Mon Nov 10 2014 at 7:17:07 PM Simon Hengel
So I would love to have tho following type class:
class Display a where display :: a -> String default display :: Show a => a -> String display = show
Note that for many Prelude types `show == display`, with the notable exception of String, where `display = id`. One use case where this matters is string interpolation [1][2][3].
I would also like a class like that to exist.
But I think it should be based on Text and Text builder rather than String (and hence be outside of base).
I created an initial draft:
https://github.com/sol/display/blob/master/src/Data/Display.hs
Is this intended to be a standalone library, or part of text (or some other package?).
I named the builder version `displayBuilder` as I could not come up with any better name (suggestions much appreciated!).
In addition, I think the `display` method has to be outside of the class. Otherwise, if somebody defines `display` he end up with the default implementation of `displayBuilder` (which is based on show and may not be what is intended). Any input on that?
I don't think this is a good enough reason to avoid a possible optimization. I'd recommend documenting this aspect of the typeclass thoroughly, and then let people shoot themselves in the foot if desired. Michael PS: I just saw Greg's email, I'd like to +1 his questions, clarification is good.