On Sun, May 17, 2015 at 7:54 AM, Peng Yu <pengyu.ut@gmail.com> wrote:

> GHCi has such a command:
> :doc <function name>
>
> For example:
> Prelude> :doc head
> Prelude head :: [a] -> a
>
> Extract the first element of a list, which must be non-empty.
>
> From package base
> head :: [a] -> a

Where is it? I don't see it.

GHCi, version 7.10.1: http://www.haskell.org/ghc/ :? for help
Prelude> :doc head
unknown command ':doc'
use :? for help.
Prelude>

I suspect the author's environment defines the doc command, as it's not built in. Links to two different ways (one that opened pages in a web browser, and the other that invoked the hoogle command) to do that have already been posted to the thread.