RE: [R] observed power

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Subject: RE: [R] observed power
From: Richards, Tom (richards@pci.upmc.edu)
Date: Mon 29 Jan 2001 - 17:35:09 EST 

Message-ID: <5B9B19C8A522D411A8EC00A0C99D6A9A02E6E6@mail.nsabp.pitt.edu>

Hello:

Here is my current version info:

platform i386-pc-mingw32
arch x86
os Win32
system x86, Win32
status
major 1
minor 2.1
year 2001
month 01
day 15
language R

I am using NT 4.0. Modifying some C code I originally did under R version
1.1.1, I find in the R Extensions manual (p. 34), that I need to change

STRING to STRING_ELT
VECTOR to VECTOR_ELT
etc.

I am using VC++ 6.0, and I simply cannot get that change to work. I am
going to just give a simple example which shows what is happening. This
example uses the getAttrib() and getListElement() functions which appear in
many source files. It works perfectly on 1.1.1, but gives an unread memory
error under 1.2.0. Am I doing something wrong here?

First, a revised getListElement function, as suggested in the manual:

static SEXP getListElement(SEXP list, char *str)
{
        SEXP elmt = R_NilValue;
        SEXP names = getAttrib(list, R_NamesSymbol);
        int i;
        for (i = 0; i < length(list); i++)
#if R_VERSION < R_Version(1, 2, 0)
                if (strcmp(CHAR(STRING(names)[i]), str) == 0)
                {
                        elmt = VECTOR(list)[i];
                        break;
                }
#else
        if (strcmp(CHAR(STRING_ELT(names,i)), str) == 0)
        {
                elmt = VECTOR_ELT(list,i);
                break;
        }
#endif
        return elmt;
}

Now, a simple calling function, called foo(), for Windows:

__declspec (dllexport) SEXP foo(SEXP input)
{
        SEXP L,V,tmp;

        input = CDR(input);L = CAR(input);
        input = CDR(input);V = CAR(input);

        tmp = getListElement(L, "b");
        return tmp;
}

I want to feed foo() a list and vector in R, so I made the R function

foo <- function(L,V){res <- .External("foo",L,V);res}

and I called

> foo(list(a=4,b=6),c(2,4,9))

This command yields 6, as it should, in version 1.1.1, but crashes version
1.2.1, with a "memory not read".

If you're still reading at this point, please note that I placed the two C
functions in a source file, and at the top I included:

#define VC

#include <math.h>
#include <R.h>
#include "Defn.h"
#include <Rdefines.h>

Is there something obvious here that I'm missing? thanks in advance.

Tom Richards
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