The Boost library, serialization, and an ampersand operator?

Question

I come from a Java and C# background and as a way to dive into C++, I'm building an icons dock using Qt and Boost. Looking at the documentation for the serialization, I stumbled uppon some interesting use of an & operator.

class gps_position
{
private:
    friend class boost::serialization::access;
    // When the class Archive corresponds to an output archive, the
    // & operator is defined similar to <<.  Likewise, when the class Archive
    // is a type of input archive the & operator is defined similar to >>.
    template<class Archive>
    void serialize(Archive & ar, const unsigned int version)
    {
        ar & degrees;
        ar & minutes;
        ar & seconds;
    }
    int degrees;
    int minutes;
    float seconds;

The purpose of the & operator is very clear reading the comments. What I'd like to know, is how is it achieved? How does it know what "&" is supposed to mean? I searched for more uses of the ampersand operator on Google, but all I can find is & used in order to denote reference rather than an opperation.

Thanks.

Overloaded bitwise-and operator (to mean something completely different). — Xeo, Jul 16 '12 at 04:07
To my eye this is an example of why overriding bitwise operators is usually a bad idea. — Crashworks, Jul 16 '12 at 04:27
There's nothing more ambiguous about this use of `&` than any other poorly-named method. — Puppy, Jul 16 '12 at 04:38

perreal · Accepted Answer · 2012-07-16T04:39:28.123

2

An example for overloading bitwise-and:

class Archive {
public:
   std::ostream& operator&( std::ostream& out ) {
       return out << to_string();
   }
   std::string to_string() { return "a string"; }
};

edited Jul 16 '12 at 04:39

answered Jul 16 '12 at 04:25

perreal

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score 0 · Answer 2 · answered Jul 16 '12 at 06:34

0

For non-builtin types, You can define operator behaviour in C++.

For details, see the C++ FAQ.

answered Jul 16 '12 at 06:34

Black

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The Boost library, serialization, and an ampersand operator?

2 Answers2