Andy Little wrote:
"Jonathan Turkanis" <technews@kangaroologic.com> wrote
Andy Little wrote:
BTW why doesnt boost::rational have a 'value_type' member rather than the obscure 'int_type'?
You'd have to ask Paul. I would guess it's mean to reflect the requirements on the template parameter.
If you are using a rational , you are kind of going to figure out that the value_type should be an integer... I hope.
It's also documented, of course. But my point was that name was chosen to suit the problem domain.
OTOH this requirement can be imposed.
However rational should be seen as one of a family of UDT value_type-operable types. (std::complex , boost::rational and boost::interval can all be Op'ed with their value_type. And in fact have a remarkably similar set of function signatures)
The nearest precedent in the standard is complex which does have a 'value_type' member. In using UDTs that implement numeric types it is reasonably common to want to know the 'value_type', for which purpose I use a to_value_type<T> function, which by default recursively inspects T::value_type for non-inbuilt types. In determining rational (and incidentally interval) value_types I have had to create specialisations which is tedious. There seems to be no particular reason not to follow the standard name for the value_type in either rational or interval.
The best way to provide a uniform interface for these types would be to provide a TR1 tuple interface. This would be compatible with keeping the name int_type. Jonathan