On 04/26/2005 05:21 PM, Joel wrote:
Larry Evans wrote: [snip]
Not if you use either something like mpl's map:
[...]
-------------------- cut here --------------------- [snip]
Gentlemen, these are all variations of the associative tuple. An implementation of fusion's set and map will be available as soon as I formalize the interface. I already have an implementation handy, ready to be deployed.
[snip]
As to which is better: a (type) tag or an enumerator; a (type) tag is definitely better because 1) an enumerator fails to address common idioms like named parameters which uses type
OK. I hadn't thought of that. I'd also been wondering why there couldn't be a boost::map_c similar to boost::vector_c whose first argument would be the integral type. This would avoid the need for the field_name nested template in my previous post.
tags. And, 2) a type tag can handle enumerators as well if you place them in some sort of enum_<enum> template akin to mpl::int_:
template <my_enum e> struct my_enum_ {};
IOTW, you can easily convert an enum to a type.
As was demonstrated with the template<enum_map_0::field_names FieldName> struct field_name{}; in the snipped part of my post which was quoted above ;) BTW, changing: [-------- cut here --------- template < class FieldTypes , class Indices
struct tuple_indexed : factor < FieldTypes , size<FieldTypes>::value > { ]-------- cut here --------- to the following: [-------- cut here --------- template < class FieldTypes , class Indices=unsigned
struct tuple_indexed : tuple < FieldTypes > { ]-------- cut here --------- in the vault code mentioned in my previous posts would work just as well and reuse boost::mpl::tuple or, I assume, fusion's tuple, and achieve what OP desires, AFAICT. If OP doesn't want to be bothered with the enum_map arg to tuple_mapped (see vault code), he could just use tuple_indexed<FieldTypes> (using the default Indices=unsigned). I haven't tried it yet.