on Wed Nov 26 2008, Eric Niebler <eric-AT-boost-consulting.com> wrote:
I've noticed an inconsistency with how the preprocessor library handles integer ranges. Consider this:
#define M0(Z,N,DATA) N BOOST_PP_REPEAT_FROM_TO(1,3,M0,~)
This treats the range 1,3 as half-open. It generates the sequence "1 2". But consider this:
#define BOOST_PP_LOCAL_MACRO(N) N #define BOOST_PP_LOCAL_LIMITS (1,3) #include BOOST_PP_LOCAL_ITERATE()
This treats the range 1,3 as closed. It generates the sequence "1 2 3".
Why the difference?
I know Paul explained his rationale for that at one point, but I don't remember what it was. If I had to guess, I'd say a closed range allows a natural and minimal implementation of vertical repetition, whereas the use of an open range would add a dependency on BOOST_PP_DEC. Total guess, though. -- Dave Abrahams BoostPro Computing http://www.boostpro.com