[R] srt --- slope text with function?

[ivo welch]

Thank you, as always.

May I disagree with you and offer a suggestion?

In the best of worlds, a function should have multiple attributes.  In
addition to the function name and its argument list, two mandatory
attributes should be a filename and lineno.  If the function is
interactively created, perhaps we can call the filename "-" and the
lineno a count that could come from the history().   Yes, it will
*NOT* be perfect, but it would be a big improvement.

If functions can have attributes, in addition to keeping the filename
and lineno,  it would be great if it could have an immediate
association with a short documentation message?  This could be a neat
documentation crutch, useful, e.g., in ls.str() or a describe().  the
best syntax that I can think of just stinks, but maybe a standard
argument does the job and should be encouraged.
  xyz <- function(args, doc="xyz returns 0") { return(0); }
I do not think the following syntax would work stylewise:
  xyz <- function "xyz returns 0" (args) { return(0); }
but it would be nicer in noting the difference between a normal
argument and a short function descriptor.

regards,

/iaw

by traceback(), do you mean the gdb() like traceback of the R
internals?  This would not be too helpful to most users.  I would be
more interested in my R call stack, not my underlying C call stack.

[and thanks again for all the other info].

regards,

/iaw



On 2/6/06, Prof Brian Ripley <ripley at stats.ox.ac.uk> wrote:

> 'Actually', R does what you ask it to: see options(error).  But before the
> program stops, there is no error to report.  In interactive use I see no
> problem in typing traceback() or using recover() (see below), but for
> batch use we are looking at alternatives.  For example, in R 2.3.0
> (modern) Unix users will get a traceback after a segfault.
>
> > There's going to be a new section on debugging in the R 2.3.0 "Writing R
> > Extensions" manual (written by Brian Ripley).  You can see it now if you
> > build R-devel (or download a binary build from CRAN; I put Windows
> > builds there approximately daily).  I also put together a
> > Windows-oriented debugging page at
> > http://www.stats.uwo.ca/faculty/murdoch/software/debuggingR/.
>
> filename+lineno makes no sense: R functions are not (in the main) from
> files.  They can be autogenerated (and often are).  And I can 'fix' them.
>
> As for the call stack, try options(error=recover) and 'where': see the
> chapter Duncan pointed you to.
>
> >> * is there a way to print all my user defined functions?  I have an
> >> init file, in which I am defining all sorts of useful utility
> >> functions, and I would like to print what I have defined (for memory)
> >> upon a read of this init file?  that is, something that has
> >> functionality like
> >>    note.all.local.definitions.now.in.vector( all.local.functions )
> >>    a <- function() { }
> >>    b <- function() { }
> >>    cat( all.local.functions ); # should print 'a' and 'b'.
> >
> > ls.str() includes an option to select only functions.  You could also
> > write your own filter for ls() output.
> >>
> >> * is there a string variable that gives me the name of the current
> >> function I am in?
> >
> > I don't think so, but sys.call() gets close.  Watch out though:  the
> > name you see will be the name used by the caller, which may not be the
> > name used when the function was written.  For example, in a function
> > called from apply(), you'll see FUN, not the original name.  Objects
> > don't know their own names in general, because they keep getting passed
> > around.
>
> In the debugging context the command 'where' tells you the sequence of
> calls (which can be more helpful).
>
> More generally, functions need not even have names (Bill Venables calls
> them 'anonymous functions'), as in
>
>      r <- sapply(nms,
>                  function(n) if (exists(n, envir = envir, mode = mode))n
>                              else as.character(NA))
>
> from ls.str.
>
>
> --
> Brian D. Ripley,                  ripley at stats.ox.ac.uk
> Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
> University of Oxford,             Tel:  +44 1865 272861 (self)
> 1 South Parks Road,                     +44 1865 272866 (PA)
> Oxford OX1 3TG, UK                Fax:  +44 1865 272595
>