I originally posted this to the wrong group, but I intended it for this
group.
I have a boost::multi_index question.
My current container has looked like the following for a very long time:
typedef
std::map
mtype_t;
What I am looking for is a way to index the mtype_t::value_type.first
value so that, syntactically,
it appears like a vector. For example, the container I need would let
me do something like:
{
container_t c;
c.insert( container_t::value_type( keycount_t( 1.414,88) ));
c.insert( container_t::value_type( keycount_t( 3.141,77) ));
c.insert( container_t::value_type( keycount_t( 23.000,99) ));
for(int index=0; index,
boost::multi_index::member<
keycount_t,double,&keycount_t::key
>
>
>
container_t;
This gives me the basics. But I cannot think of a way to add a
secondary index that would give me the O(1) vector-like indexing. A
use-case of the grammar I am after would be something like the following:
void useless_function(container_t& c)
{
for(container_t::iterator i = c.begin(); i!=c.end(); ++i)
print("key=%f\tval=%d\n",i->first,i->second);
for(index=0; indexsecond);
}
Here's WHY I need this: I have a stream of floating point values coming
in (fixed to 5 significant digits). I need to keep count of how often
any one of the floating point values is repeated. Very often I need to
respond to requests as to the contents of the container at the Nth
position. The slow O(n) method would be:
const keycount_t& get_nth_record(int index,const container_t& c)
{
container_t::const_iterator i;
for(i=c.begin(); i!=c.end(); ++i)
if(--index==0 )
break;
return( *i );
}
But again, I need O(1) time, so I need some sort of index added to my
container_t.
Has anyone done this sort of thing before, and met the O(1) positional
index requirement?
Many thanks!
-zap
