符号表达流I/O.

Question

在Common Lisp中,如何从/向流读取和写入符号表达式？例如,我可能想要写一个匿名函数来文件,然后读取并执行它:

;;; sexp-io.lisp
;;; Try writing a sexp to file and reading it back in

(with-open-file (file "~/Documents/Lisp/Concurrency/sexp.lisp"
                  :direction :output :if-exists :supersede)
  (print #'(lambda () (+ 1 1)) file))

(with-open-file (file "~/Documents/Lisp/Concurrency/sexp.lisp"
                  :direction :input)
  (read file))

但是,该代码导致可疑输出

 #<Anonymous Function #x3020018F950F>

当我尝试将其读回时会导致错误:

> Error: Reader error on #<BASIC-FILE-CHARACTER-INPUT-STREAM ("/Users/frank/Documents/Lisp/Concurrency/sexp.lisp"/7 UTF-8) #x3020018F559D>, near position 3, within "
>        #<Anonymous ":
>        "#<" encountered.
> While executing: CCL::SIGNAL-READER-ERROR, in process Listener(4).

Answer 1

你正在做TRT,除了#'把它变成一个对象.只需用一个简单的引号(读作为)替换sharp-quote(读作),它应该可以工作.list (lambda () (+ 1 1))functionfunctionquote

你可能想使另一个变化是更换print与write带有参数:readably t:

(write my-object :stream out :readably t)

好处:readably是,如果它不能以保持打印读取一致性的方式写入,它就会失败.