[R] how to get code of a .Internal() function?

[Duncan Murdoch]

This is really an R-devel question, but R-help readers may have wondered 
about this.

Alban wrote:
> Hello,
> 
> I'm working with the function optim() from stats
> package,
> and inside this function is called the function
> .Internal(optim(....)) and I want to get the code of
> this function which would help me to understand why
> the Nelder-Mead algorithm doesn't converge with my
> data.
> I'm working under Windows XP.
> Could you reply to this adress because I don't belong
> to the mailing list
> Thank you very much!!!

.Internal functions are written in C.  Many users won't have the C 
source installed; you'll need to go to CRAN to get it.

The source for .Internal functions is usually (always?) somewhere in the 
src/main subdirectory of the source tree.  You find it by looking up the 
identifier in src/main/names.c, finding this line:

{"optim",	do_optim,	0,	11,	7,	{PP_FUNCALL, PREC_FN,	0}},

which tells you that the do_optim routine handles this stuff.  Further 
searches would show you that this function is defined in src/main/optim.c.

Duncan Murdoch