"Found hole"

[Brandon Allbery]

On Tue, Jan 20, 2015 at 1:36 PM, Volker Wysk <verteiler at volker-wysk.de>
wrote:

> What is a "hole"?


https://downloads.haskell.org/~ghc/latest/docs/html/users_guide/typed-holes.html

When I replace "_exit" with "foo", it produces a "not in scope" error, as
> expected. What is special about "_exit"? It doesn't occur in the Haskell
> Hierarchical Libraries.
>

The leading underscore invokes the typed holes extension. If you want to
use such names, you'll need {-# LANGUAGE NoTypedHoles #-} as the first line
of the source file. (I am not sure why this extension was enabled by
default.)

-- 
brandon s allbery kf8nh                               sine nomine associates
allbery.b at gmail.com                                  ballbery at sinenomine.net
unix, openafs, kerberos, infrastructure, xmonad        http://sinenomine.net
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