template specialization for unsigned types

[bloer]

Hello all,

First, some mostly gratuitous background, which you can safely skip if you're not interested, or feel free to comment/give suggestions:
I am writing a configuration interface for a DAQ system which reads in text-based configuration files. Because of the large number of parameters which might need to be set and their grouping into a nice tree-like structure, I've created a ParameterNode class, which holds a map<string,ParameterNode*> of all that node's children (or branches, leaves, whatever). Then to store simple variables, there is a templated Parameter<class T> class which inherits from ParameterNode. This allows me to have arbitrarily complex parameter structures without having to re-write any of the iostream interface.

So here's the problem. My Parameter class looks like

template<class T> Parameter{
public:
     Parameter(const T& val) : _val(T) {}
     ~Parameter() {}
     std::istream& ReadFrom(std::istream& in) { return in>>_val; }
     std::ostream& WriteTo(std::ostream& out) { return out<<_val; }
private:
     T _val;
};
 

Now, I'd like to have any unsigned values be written/read with the form 0x1EF8, etc, i.e. turn on hex and showbase. So for instance I'd get something like

template<> inline std::istream& Parameter<unsigned>::ReadFrom(std::istream& in)
{
  in>>std::hex>>std::showbase>>_val>>std::noshowbase>>std::dec;
}

So, will this work for any unsigned type, or do I have to declare separate instantiations for all of unsigned, unsigned char, unsigned short, unsigned long, uintX_t, etc?

Many thanks,
~Ben

[arnaudk]

"unsigned" is a synonym for "unsigned int" so yes you'll have so specify the different specializations explicitly if you want different behavior from signed types, or just don't specialize if it's all the same anyway. You might want to take a look at boost traits which you can use to determine if a type is unsigned.

[bloer]

Thanks! Is there anything Boost can't do? Unfortunately I'm trying to minimize dependencies, so I don't want to include Boost. I noticed that the type_traits headers are also in the tr1 package which should be on most systems, but it doesn't seem to want to compile (well actually it's only linking that's the problem) on my system.

Oh well, I guess specifying them all by hand is is not so bad.