common lisp 的宏 TYPECASE

gistfile1.txt

语法
  typecase keyform {normal-clause}* [otherwise-clause] => result*

参数和值
  keyform --- 一个 form, 会被求值去产生一个 test-key

描述
  待补充

代码
  * (defun what-is-it (x)
   (format t "~&~S is ~A.~%"
           x (typecase x
               (float "a float")
               (null "a symbol, boolean false, or the empty list")
               (list "a list")
               (t (format nil "a(n) ~(~A~)" (type-of x))))))
  WHAT-IS-IT

  * (map 'nil #'what-is-it '(nil (a b) 7.0 7 box))
  NIL is a symbol, boolean false, or the empty list.
  (A B) is a list.
  7.0 is a float.
  7 is a(n) (integer 0 4611686018427387903).
  BOX is a(n) symbol.
  NIL