On 6/19/05, Rob Lopaka Lee <[EMAIL PROTECTED]> wrote: > I'm interfacing to C code that uses 1-based indexing on arrays -- it > ignores the zeroth element. Thus, input vectors from R must be moved up > one, and output arrays must be moved down one. > > What is the best way to deal with this using R internal code?
If the C code can be relied upon to ignore the zero'th element of the array then write a wrapper that gets the array, say int v[], from R and passes &v[-1] to your C code. That has the effect of shifting all the addresses back by one position. > My current approach is: > > For an input R vector of length n, allocate a new vector(v) of length n+1 > and copy input into v[1] to v[1+n]. Call with new vector. > > For an output array(a) of length n, allocate a new vector of length n-1 > and copy a[1] to a[n] into v[0] to v[n-1]. > > If this is the best approach, is there an idiom for copying vectors? In C you could use the memcpy function or the Memcpy macro defined in <R_ext/RS.h>. ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
