We enjoyed having wpdocs around, but it's been too hard for us to maintain. We're sorry to see it go.
If you need to look up a function, there's lots of information on the Codex.
Plus, all of the documentation was drawn from WordPress's source code - so you can always have a dig around there.
If you see this and you're sad that wpdocs has gone, do drop us an email: contact [at] dxw.com