How to properly ask an input from user in LispWorks?

Question

I have this code:

(defvar x)
(setq x (read))
(format t "this is your input: ~a" x)

It kinda work in Common Lisp but LispWorks it is showing this error:

End of file while reading stream #<Synonym stream to
*BACKGROUND-INPUT*>.

I mean I tried this: How to read user input in Lisp of making a function. But still shows the same error.

I hope anyone can help me.

Answer 1

You probably wrote these three lines into Editor and then compiled it.

So, you can write this function into Editor:

(defun get-input ()
  (format t "This is your input: ~a" (read)))

Compile Editor and call this function from Listener (REPL).

CL-USER 6 > (get-input)
5
This is your input: 5
NIL

You can also use *query-io* stream like this:

(format t "This is your input: ~a" (read *query-io*))

If you call this line in Listener, it behaves like read. If you call it in Editor, it shows small prompt "Enter something:".

As you can see, no global variable was needed. If you need to do something with that given value, use let, which creates local bindings:

(defun input-sum ()
  (let ((x (read *query-io*))
        (y (read *query-io*)))
    (format t "This is x: ~a~%" x)
    (format t "This is y: ~a~%" y)
    (+ x y)))

Consider also using read-line, which takes input and returns it as string:

CL-USER 19 > (read-line)
some text
"some text"
NIL

CL-USER 20 > (read-line)
5
"5"
NIL