nathanmarz/cascalog — pull request #183 by MichaelDrogalis (2013-08-30 17:57:24+00:00)
Title: Adds nil-safe aggregates.

Mirrors of functions that normally blow up when they counter nil.
Instead, these passively discard nil values.

We avoided the convention of prefixing the function with `!` and used it as a suffix.
Cascalog 2 errored on the query when it was prefixed.