Guillaume, Your questions are very legitimate. At some points it is argued that it is better to store the sign separate from the absolute value. As the absolute value is non-negative, there is no choice between ones and twos complement. I will make a remark in these member functions about this. This way the results of these member functions are indifferent to sign, and do not depend on machine word size. The counting starts with bit number 0. So is_odd now becomes lowest_bit() == 0. Sub integers exceeding the highest bit are of course as if the integer is padded with zero bits. With the current memory sizes, in my opinion the factor 8 is not purely theoretical. This way I also keep the migration to 64-bit out of my design, except of course for the integer_allocator class. Regards, Maarten. "Guillaume Melquiond" <guillaume.melquiond@ens-lyon.fr> wrote in message news:1148649293.19309.52.camel@saline... Le vendredi 26 mai 2006 à 14:08 +0200, Maarten Kronenburg a écrit :
As a response for a request for sub integers, in the document I will delete the is_even and is_odd member functions, and add: const integer highest_bit() const; const integer lowest_bit() const;
In my opinion, is_odd and is_even have a clearer meaning. When I read lowest_bit and highest_bit, a lot of questions come to my mind: Are they implementation-defined? Or are they the lowest and highest bits in a sign-magnitude representation of integers? Or is it a 2's complement representation? Or maybe a 1's complement representation? Is the highest bit of a positive integer always 1? Or will its value depend on the machine word size and the integer size? Do these functions really have to return an integer?
const integer get_sub( const integer &, const integer & ) const; By the way here no size_type is used, because size_type suffices for the range of bytes, but not for the range of bits, which is a factor 8 larger.
Same kind of question here: this member extracts a sub-integer with respect to which representation? For example, what does a sub-integer of a negative integer look like? Also I wouldn't worry too much about size_type being too short by a factor 8 :-). Somebody who really needs to use integers that long will probably use its own hand-crafted classes in order to be sure a library will not do any memory allocation to store them. Sorry if all these questions were already answered in your draft and I failed to find it. Best regards, Guillaume _______________________________________________ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost