common lisp 的函数 INPUT-STREAM-P, OUTPUT-STREAM-P

input-stream-p-vs-output-stream-p.txt

语法
  input-stream-p stream => generalized-boolean
  output-stream-p stream => generalized-boolean
  

参数和值
  stream --- 一个 stream
  generalized-boolean --- 一个 generalized-boolean

描述
  input-stream-p 如果 stream 是一个 input-stream ,返回 true, 否则返回 false
  output-stream-p 如果 stream 是一个 output-stream ,返回 true, 否则返回 false
  
代码
  * (input-stream-p *standard-input*)
  T

  * (input-stream-p *terminal-io*)
  T

  *  (input-stream-p *standard-output*)
  NIL

  * (output-stream-p *terminal-io*)
  T

  * (output-stream-p *standard-output*)
  T
  
  * (output-stream-p (make-string-input-stream "jr"))
  NIL