Return reach of host h, as defined by RFC 2965, section 1.
The reach R of a host name H is defined as follows:
- If
- H is the host domain name of a host; and,
- H has the form A.B; and
- A has no embedded (that is, interior) dots; and
- B has at least one embedded dot, or B is the string "local".
then the reach of H is .B.
- Otherwise, the reach of H is H.
>>> reach("www.acme.com")
.acme.com
>>> reach("acme.com")
acme.com
>>> reach("acme.local")
.local