Undocumented features of 'browser' (and possible changes)

"Kevin Wright" <kwright68 at gmail.com> writes:

I often use browser() when debugging a function.  After entering
browser, I would find it very useful to be able to cut-and-paste a
chunk of R code to the browser (or use ess-eval-region in Emacs).  An
inconvenience, however, is that both blank lines and comment lines
will exit the browser.

The man page for browser says nothing about exiting the browser via
ENTER or via a line that begins with a comment, only that
"sub-interpreter can be exited by typing c" and "Typing Q quits the
current execution".

A hack that does allow code pasting into the browser is to put "NULL"
at the start of blank lines and comment lines.

Question: How would people react to a request to change the browser so
that blank lines and comment lines do not exit the browser?

Possible answers (check one or write your own)
[ ] - Who are you kidding?
[ ] - Even though it is undocumented and redundant, I use ENTER to exit browser
[x] - You are forgetting about this scenario...

ENTER does not actually quit the browser, it repeats the last command,
as in

f(2)

Called from: f(2)
Browse[1]> n
debug: x <- 2
Browse[1]>
debug: y <- x + 1
Browse[1]>

This is useful, since it drives you nuts to type "n",ENTER if you're
debugging a lengthy piece of code (possibly more noticeable when
you're using debug() than with browser(), but the two need to be
consistent). This is also the way things work in e.g. the gdb
debugger.

Having "c" as the initial default is still open for discussion, of
course. The scenario where browser() is in a function that gets called
repeatedly does require some attention; it might be convenient to be
able to continue with a single keystroke in that case.

[ ] - A patch would be welcome
[ ] - Sounds great and I committed the changes already.  :-)


Kevin Wright, Windows 2000, R 2.2.1

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