Erlang has guard sequences, also a "when" clause: http://erlang.org/doc/reference_manual/expressions.html#id83710 http://erlang.org/doc/reference_manual/express

Erlang has guard sequences, also a "when" clause: http://erlang.org/doc/reference_manual/expressions.html#id83710 http://erlang.org/doc/reference_manual/expressions.html#id83...