[R] lang2(...) with two and more arguments

[Douglas Bates]

Timur Elzhov <Timur.Elzhov at jinr.ru> writes:

> On Tue, Nov 03, 2003 at 17:06:37 +0100, you  wrote:
> 
> >>      REAL(x)[0] = 10;
> >>      REAL(y)[0] = 20;
> >>      SETCADR(R_fcall, x);
> >>      SETCADR(R_fcall, y);
> >>      ...
> >>  .Call("f", c, new.env()) returns
> >>  `.Primitive("c")(20)'
> > Hmmm. This is definitely not right:
> > 
> >      SETCADR(R_fcall, x);
> >      SETCADR(R_fcall, y);
> > 
> > sets the same location first to x, and then to y. I suspect you need 
> > 
> >      SETCADDR(R_fcall, y);
> > 
> > but no guarantees...
> This returns message `bad value'.
> 
> Ok! the question is: How can I create a call with, say, 10
> arguments? I mean C code, of course :)

Better look at your example more closely.  lang2 is used to create a
function call with *one* argument.  lang2 itself takes two arguments:
the name (i.e. an SEXP of type name) of the function and an SEXP to
the argument.

You create a function call of two arguments with lang3 and a function
call of three arguments with lang4.  After that I think you have to
cons up a (lisp-like) list yourself.

This discussion probably belongs on r-devel not r-help.