input-port? -- vonuvoli Definition predicate;
input-port? (from r7rs);Procedure variants:
((input-port |1...|) -> (true))
input-port;... -- at least one time;true;((port |1...|) -> (false))
((any |1...|) -> (false))
vs:io -- (vonuvoli io);input-port;true;port;false;any;