On 17/08/15 15:36, Jonathan Wilkes via Pd-list wrote:
> Hi list,Wondering if someone will give me a free lesson in C programming.
> In g_traversal.c, there's some code to retrieve a float from a t_word* vec.  It looks like this:
> *(t_float *)(((char *)vec) + onset));
> Why does vec need to be cast to char*?  t_word has to be as big as the largest member of the union, and the largest member has to be the same size as char*, right?  (Otherwise we'd have big problems...)

aiui pointer arithmetic is in increments of sizeof(pointee)
if onset is measured in bytes (I don't know if it is in this case, but
it looks likely), then you need to have a pointer to bytes for the
addition to be meaningful.  vec is already a pointer, but adding onset
to a t_word* would offset the address by onset*sizeof(t_word) bytes