[boost] Tagged typedef

From: Maksym Motornyy (mmotorny_at_[hidden])
Date: 2005-06-01 04:55:57

Hi all,

It is know that typedef in C++ is actually an alias, i.e. it doesn't 
create new distinguishable type. Sometimes this causes problems. 
Consider following example:

typedef int handle;

template < typename Value >
void write( const Value &value );

void write< int >( const int &value )
{
     // do processing for int
}

void write< handle >( const handle &value )
{
     // we wanted to have separate processing for handle,
     // but we get only compilation error :(
}

In my projects I resolve such situations as the following:

class handle_tag
{
};

typedef tagged< int, handle_tag > handle;

Then everything works as expected. "tagged" class is actually a wrapper 
that mimics fundamental type behaviour. Also I have specialization for 
pointers.

Is anyone interested in such solution of given problem? Is it worth to 
be part of Boost?

Sincerely,
Maksym Motornyy.