>>>>> I V <ivle...@gmail.com> (IV) wrote: >IV> On Fri, 10 Jul 2009 16:27:12 -0400, Terry Reedy wrote: >>> a bug, bug a limitation due to using limited-range numbers. If one uses >>> residue classes instead of integers, and makes no adjustment, I consider >>> it wrong to blame Bentley.
>IV> But it was Bentley himself who used the C int type, so it hardly seems >IV> unreasonable to blame him. If you are on a 32-bit machine, and the array to be searched contains ints, floats or doubles, the the array must be < 2^32 bytes in size, and as each element is at least 4 bytes, the indices are less than 2^30, so l+u < 2^31. Therefore there is no overflow at all. I think the Bentley programs were formulated in terms of arrays of ints. So his implementations were safe. If you are on a 64-bit machine you shouldn't use int for the indices anyway (supposing int is 32 bits) but longs and then the same reasoning shows that there are no overflows. Only when you have an array of shorts or bytes (chars) you get the problem. In that case the alternative formulation l + (u-l)/2 is more robust and therefore preferable. -- Piet van Oostrum <p...@cs.uu.nl> URL: http://pietvanoostrum.com [PGP 8DAE142BE17999C4] Private email: p...@vanoostrum.org -- http://mail.python.org/mailman/listinfo/python-list
