[R] Attempting to access an R list from within C code

From: Cormac Long <clong150_at_googlemail.com>
Date: Wed, 27 Apr 2011 14:43:54 +0100

Hello R-help,

I am wondering if anyone can help me with this:

I want to access data in a list which has been passed into a C function, but I cannot work out how to access the values. How do I move from the given SEXP pointer to the next object in the list? I have tried to use CDR, but to no avail. The following code gives an

    'address (nil), cause unknown'

R Code:

C Code (kept in file thelib.c, compiled on Ubuntu x64 machine using R2.13.0):

void showList(SEXP *obj, int *size)
  SEXP *locObj=obj;
  int i;
    Rprintf("Entry is %d: value is %f",i,REAL(*locObj)[1]);     *locObj=CDR(*locObj);

Any help is greatfully appreciated!
Best wishes,
Dr. Cormac Long.

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