alphashapes2d can handle degenerate inputs (thanks to Taras Galkovskyi for the bug report and the fix)
From: Dmitriy Morozov <morozov@cs.duke.edu>
Date: Wed, 27 Feb 2008 16:30:57 -0500
State: fixed
Subject: Segfault with topology/vineyard log enabled
Message-Id: <d2ab07329c3588ca-0-artemis@metatron>
The code segfaults in Vineyard::record_knee() if we subscribe to
topology/vineyard log.