[slime-devel] Weird one to do with pretty-printing

[Helmut Eller]

Peter Seibel <peter at javamonkey.com> writes:

> Okay, this one is quite strange. First define this function:
> 
>   (defun foo ()
>     (write (macroexpand-1 '(with-open-file (in "foo.txt") (read in))) :pretty t))
> 
> Then invoke it several times. What I observe is that the body of the
> let moves to the right each time I invoke FOO, as if the
> pretty-printing stream is somehow preserving some information about
> what column it is indenting to from call to call. I believe I had
> observed this behavior before when I was screwing around with
> pretty-printing logical blocks. This weird shifting only happens in
> the SLIME repl, the same function invoked from the *inferior-lisp*
> buffer works as expected. I've observed this in both OpenMCL and in
> Allegro on GNU/Linux.

Yes the stream preserves the column.  The reason you don't see this
behavior in the *inferior-lisp* is that Lisp prints the prompt with a
newline character and this resets the column.  SLIME inserts the
prompt at the Emacs side without printing any newline to the stream.

I will try to find a way to reset the column.

Helmut.