LISP I/O Hints


use READ
    READ-CHAR
    READ-LINE
for input
and FORMAT 
for output.
    PRINT and PRIN1 are also available but less useful.

--------------

To change between char and string data types try COERCE 

--------------

Steele's lisp book. Common Lisp the Language, 2nd Edition 
via class web page. 

describes  OPEN  and WITH-OPEN-FILE and CLOSE for file I/O

"Because with-open-file always closes the file, even when an error
exit is taken, it is preferred over open for most applications." 

-----------


(WITH-OPEN-FILE (output-stream output-file
		     :direction :output
		     :if-exists :new-version
		     :if-does-not-exist :create)
      (WITH-OPEN-FILE (input-stream input-file
	         	     :direction :input)
            (FORMAT output-stream "~a" (READ input-stream nil))
)     )


the value of output-file and input-file should be a string.
You might be able to get away with just the file name
e.g.,   "rules.lsp"   
but you might need a path "/users/csfaculty/dcb/ai/proj1/rules.lsp"

Using (READ input-stream nil) will a value of NIL at end of file. 
Using (READ input-stream nil 'eof) will return the symbol eof at the
end of the file. 

Note that (FORMAT t  ...  ) prints to terminal (i.e. to screen).

Note that the  :if-exists :new-version
	       :if-does-not-exist :create
stuff is optional. 

-------------

(WITH-OPEN-FILE (input-stream "dcb.in"
         	     :direction :input)
   (READ input-stream nil)
)  

(WITH-OPEN-FILE (output-stream "dcb.out"
		     :direction :output)
   (PRINT '(a b c d)  output-stream)
)


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Wed Sep 13 22:13:04 EDT 2000