[Rd] book for the reluctant C programmer

[Tamas K Papp]

Dear R experts,

I have started recoding bottlenecks of my R program in C.  When doing
so, I realized that my C knowledge is a bit rusty: the last time I
used (or dabbled in) this language was 12 years ago, and I seem to
have forgotten quite a bit, and the language also evolved since.

Please recommend books for brushing up on my C knowledge, if possible,
ones that are clear and use recent C like C99 (if you think that makes
sense).  I only expect to write 10-20 line routines to be called from
R, but I think that having clear concepts and foundations would help
me do it better.

Thanks,

Tamas