In my opinion the unsigned integer with a modulus is required, which is generalizing the base type unsigned int (which is modular) to any modulus. So the unsigned_integer would have a static method void set_modulus( const integer & ). The only problem is what an unsigned_integer is when a modulus is not providid, that is when the modulus is zero. Then I propose that as the user did not provide any modulus, only in this case negating a non-zero unsigned_integer will be an error. Also I propose that such an unsigned_integer will be provided by implementations, and be added to the specification. "Maarten Kronenburg" <M.Kronenburg@inter.nl.net> wrote in message news:e5c7h0$vht$1@sea.gmane.org...
Perhaps we have to specify such an unsigned (modular) integer so that implementations can provide it. Such an unsigned_integer would then have a static method set_modulus( const integer & ). Then I should merge the unsigned_integer and modular_integer into unsigned_integer in the document. I will refer to [expr.unary.op] item in any case.
Beman Dawes wrote:
That isn't correct, AFAICT. An unsigned does support unary negation.
5.3/9 says "The operand of the unary - operator shall have arithmetic or enumeration type and the result is the negation of its operand. Integral promotion is performed on integral or enumeration operands. The negative of an unsigned quantity is computed by subtracting its value from 2n, where n is the number of bits in the promoted operand. The type of the result is
"Sebastian Redl" <sebastian.redl@getdesigned.at> wrote in message news:4478BF17.7020404@getdesigned.at... the
type of the promoted operand."
The operator exists, but only for the language unsigned integers, which aren't really unsigned integers, but modulo integers, as is obvious from the definition of the negation. The same definition is impossible for a (theoretically) infinite-precision integer, because, lacking a number of bits in the representation (n), there is no 2^n from which can be subtracted.
Sebastian Redl _______________________________________________ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost
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