BurntSushi/erd — pull request #3 by eric-brechemier (2014-09-01 11:03:03+00:00)
Title: Fix symbol (syntax) used for cardinality of 0

When using '0' as described in the README so far,
the following error is reported:

unexpected "0"
expecting relationship

(using erd installed from cabal today).

I tried '?', by consistency, which worked,
and checked the source code, which reads:

let ops = "?1*+"

leaving no doubt.