[Haskell-cafe] RFC: in haddock, collapse instances by default

Ian Denhardt ian at zenhack.net
Thu Jan 3 05:23:58 UTC 2019

Quoting Li-yao Xia (2019-01-02 11:18:41)

> For a motivating example, I can point to the Prelude we all love.
> https://hackage.haskell.org/package/base-
> We are immediately welcomed by half a page of instances of Bool, which
> is not quite bad, but classes have the most impressive instance lists,
> as you may see when you reach Eq.
> Many packages, even commonly used ones, have the same issue. For an
> extreme example, see the scrollbar jump when you fold the instance
> list of Apply in singletons.
> https://hackage.haskell.org/package/singletons-2.5.1/docs/Data-Singletons.html#t:Apply

Another example where this gets a little ridiculous is my capnp package,
which defines a few type classes with instances for most types in the
generated code, e.g:


It's not quite as absurd as the singletons package, but from eyeballing
the size of my scrollbar I'd guess that the instance lists are 80-90% of
that page.

> Of course, instance lists also contain quite important information.
> Would it become too easy to miss if it were hidden by default? Would a
> more fine-grained alternative be better?

Personally I rarely use them.

It was mentioned on the Github issue/pr as well, but I think a
collapse/expand all would be a good idea. My personal inclination would
be to have it collapsed by default, though I feel less strongly about


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