The following bug has been logged on the website:
Bug reference: 7807
Logged by: Andrei Rares
Email address: a_rares(at)yahoo(dot)com
PostgreSQL version: 9.1.7
Operating system: GNU/Linux 3.2.0-35-generic x86_64
Description:
In the documentation
(http://www.postgresql.org/docs/9.1/static/functions-math.html) it is
written that the return type is the same as the input, but a query like
'select sign(1::int)' returns a double