Hi Mark, Mark H Weaver <m...@netris.org> writes:
> l...@gnu.org (Ludovic Courtès) writes: >>> Why do you think the C interface should be kept internal? Most of the >>> core arithmetic procedures provide public C interfaces. Why should >>> exact-integer-sqrt be treated differently? >> >> Because: >> >> 1. I think we shouldn’t augment the C API unless strictly necessary, > > We recently added several convenience functions that weren't strictly > necessary. Do you think that was a mistake? As I said, I wasn’t fond of it. However, it’s true that C code often has to deal with modules to glue things together, so I can understand that it makes people’s lives easier. > The function in question (which computes the exact floor of the square > root along with the remainder, analogously to the number-theoretic > division operators) is not part of the standard C library, and is not > entirely trivial to implement efficiently in the general case, when > bignums are included. I can easily imagine that a program might want to > use this function from C. If we don't provide this interface, there > will be no efficient way to access it from C. OK. I was thinking that I’d use C when dealing with fixnums or floats, and let Guile manage bignums and similar—in which case writing C doesn’t seem to help much. Do you think there are use cases for using this interface from C? (It’s a real question, I thought “no”, but I may be wrong.) > Unless we do not wish to support the R6RS, we have no choice but to > maintain this function indefinitely. It is true, we could in theory > eliminate the C implementation at some point in the future, but that > would be rather inefficient. Oh, I’m fine with having a C implementation of this function; I was just wondering whether the C function should be public. >> 2. This particular function is “unusual” in that it returns ‘void’ and >> takes pointers to SCM. > > This is the same style of C interface we provide for the new set of > number-theoretic division operators that return both quotient and > remainder, scm_floor_divide et al. Wingo requested that this be the > preferred C interface for returning multiple values, in order to avoid > unnecessary heap allocation. In fact, he wisely objected to my division > operator patches until I modified them to use this style of interface. OK, understood. It’s true that ‘scm_values’ sucks, but then if when can avoid exposing to C functions that return multiple Scheme values, all the better! :-) What do you think? Thanks, Ludo’.
