[plt-scheme] paired braces in interaction mode?

On Tue, Mar 4, 2008 at 9:03 PM, Grant Rettke <grettke at acm.org> wrote:
>  I don't really understand how this feature is supposed to work or why
>  someone would want it, though the folks in the thread understand, so I
>  was hoping there would be a place in the manual that would explain
>  this feature.

"it was a convenient feature of the interaction mode when a
previously evaluated S-expression could be copied into editing position by
putting a cursor on this expression and pressing enter."

*That* is what I didn't understand, though somehow I managed to
totally confuse myself and perhaps others.

After downloading 3.99.0.17-svn4mar2008 and seeing what S-expression
matching meant (the obvious of course but somehow I didn't get it) I
looked at this feature of hitting enter and copying.

Here is how it works, in the repl type:

(+ 1 2)
hit enter
(+ 1 2
;; now move the cursor up to the RIGHT parentheses of the previous
expression and hit enter
;; you end up with
(+ 1 2 (+ 1 2)

That should be mentioned somewhere in the user guide or no one will
ever use the feature.