[Rd] non-API entry point Rf_findVarInFrame3 will be removed

[iuke-tier@ey m@iii@g oii uiow@@edu]

The non-API entry point Rf_findVarInFrame3 used by some packages will
be removed as it is not needed in one use case and not working as
intended in the other.

The most common use case, Rf_findVarInFrame3(rho, sym, TRUE), is
equivalent to the simpler Rf_findVarInFrame(rho, sym).

The less common use case is to test for existence of a binding with

     findVarInFrame(rho, sym, FALSE) != R_UnboundValue

The intent is that this have no side effects, but that is not the
case: if the binding exists and is an active binding, then its
function will be called to produce a value. This usage should be
replaced with R_existsVarInFrame(rho, sym).

R_existsVarInFrame has been marked as part of the experimental API.
It is not yet clear whether Rf_findVarInFrame will become part of an
API.  If it does, then its semantics will likely have to change; if it
does not, an alternate interface will be provided.

Best,

luke


-- 
Luke Tierney
Ralph E. Wareham Professor of Mathematical Sciences
University of Iowa                  Phone:             319-335-3386
Department of Statistics and        Fax:               319-335-3017
    Actuarial Science
241 Schaeffer Hall                  email:   luke-tierney using uiowa.edu
Iowa City, IA 52242                 WWW:  http://www.stat.uiowa.edu