I was trying to understand some of the source in optimi.c and in the SANN
source I see:
SETCADR(OS->R_gcall, x);
PROTECT_WITH_INDEX(s = eval(OS->R_gcall, OS->R_env), &ipx);
REPROTECT(s = coerceVector(s, REALSXP), ipx);
if(LENGTH(s) != n)
error(_("candidate point in optim evaluated to length %d not %d"),
LENGTH(s), n);
I think I need a little help it it is not too much to ask. Admitedly I could
search for the definition of each of these macros and after some time decipher
their meaning. But in an effort to save some time I am appealing to this group.
First,
SETCADR(OS->R_gcall, x);
I was unable to find thie function call in the sources it seems to be called
everywhere so searches turn up many hits.
Second,
PROTECT_WITH_INDEX(s = eval(OS->R_gcall, OS->R_env), &ipx);
I am assuming that this acutall calls the function pointed to by R_gcall. But,
I am not sure where &ipx fits in and what PROTECT_WITH_INDEX does. I read the
"wirting exstensions" documentation and this specific macro is dealt with in
section 5.9.1 but I still am having a hard time understanding what is
happening. Perhaps the added call to eval is confiusing me. I am assuing that
this makes the function call.
Third,
REPROTECT(s = coerceVector(s, REALSXP), ipx);
Again the vector ipx shows up. Would someone please help me to understand what
this statement is doing?
Thank you for your time and patience.
Kevin
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