R help - Jan 2003 - Arguments of R- and C-side of internal functions

Dear R experts,

I looked at the body of, say, `optim' function and found
the call to the `.Internal', C optim function. It looks
like this:

  .Internal(optim(par, fn1, gr1, method, con, lower, upper))

On the other hand, the C prototype of optim is:

  SEXP do_optim(SEXP call, SEXP op, SEXP args, SEXP rho);

So, I guess that all the list of parameters passing in R are assigned
to `args', right?

First, how is that implemented?  I looked at the `.Call()' - as I
  understand, it requires for C-side the same number of parametrs
  (minus the function name to be called); and `.External()' - it
  wants the single list.
Second, who pass the other, `call', `op' and `rho' parameters
  to `do_optim() ?'


Thank you!

  
--
WBR,
Timur

Timur Elzhov <Timur.Elzhov at jinr.ru> writes:
> Second, who pass the other, `call', `op' and `rho' parameters
>   to `do_optim() ?'
You mean "why" I suppose.

op: Some functions are mapped into the same C function (do_math2, for
example) so you need to know which one.

call: The whole call is passed mainly for the benefit of error
printouts. It is not always possible to reconstruct it from the other
arguments, since "op" may be computed as in get("+")(2,2).

rho: this is the evaluation environment, and it is crucial for
variable lookup etc.

-- 
   O__  ---- Peter Dalgaard             Blegdamsvej 3  
  c/ /'_ --- Dept. of Biostatistics     2200 Cph. N   
 (*) \(*) -- University of Copenhagen   Denmark      Ph: (+45) 35327918
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