■
(if x foo) = (if (listp (listp x)) foo)?
http://www.geocities.jp/m_hiroi/
http://xyzzy.s53.xrea.com/wiki/index.php?%BA%B4%CC%EE%2Flisp%A4%CE%B3%D8%A4%D3%CA%FD
(if x foo) = (if (listp (listp x)) foo)?
http://www.geocities.jp/m_hiroi/
http://xyzzy.s53.xrea.com/wiki/index.php?%BA%B4%CC%EE%2Flisp%A4%CE%B3%D8%A4%D3%CA%FD