[R] Line numbers in error messages

[Duncan Murdoch]

On Mon, 12 Apr 2004 15:20:58 -0700, you wrote:

>Hi Patrick,
>
>>It's very simple using a browser() line in your function somewhere you
>>know your code's OK, then run line by line.  
>>
>The problem is that sometimes you have code of a few hundred lines, to 
>which you have added a strange little line that craps out because of 
>some silly mistake that would be apparent if you knew which line to look 
>at.  However....  you don't want to start inserting browser statements 
>inside the code, hoping to get close, you just want to know what line 
>caused the issue.

This is something that's on my wish list too, but it would require
fairly low-level changes.  Right now the parser doesn't record source
file information on a line, so there's no way an error message could
report it.

It's not absolutely obvious how to do it, either:  code can come from
files, from saved images, from stuff you typed at the console prompt,
from a connection, as the result of evaluating an expression, etc.
It's a lot more complicated to do this in an interpreted language like
R than in a compiled language.

Duncan Murdoch