NAME

BinopsBase - Class template offering class-type binary operators

SYNOPSIS

#include <bobcat/binopsbase>

DESCRIPTION

Classes may overload binary operators. A class named Derived may overload binary operators to suit its own needs. It could, e.g., allow two Derived class objects to be added together, or it could define a shift-operation given a size_t right-hand side (rhs) argument.

The available binary operators are *, /, %, +, -, <<, >>, &, |, and ^ (in this man-page they are generically indicated as the `@’ operator). In addition, overloaded operator<< and operator>> for stream insertion and extraction are frequently defined.

If a class Derived supports copy and/or move construction and if it offers a swap member (void Derived::swap(Derived &rhs)), and is publicly derived from FBB::BinopsBase<Derived> then once Derived defines a member

    void Class::operator@=(Rhs const &rhs) &&


        

    Derived &operator@=(Rhs const &rhs) &


    Derived operator@(Derived &&lhs, Rhs const &rhs);


    Derived operator@(Derived const &lhs, Rhs const &rhs);


        

A similar procedure applies to the insertion and extraction operators. Insertion and extraction operators become available once BinopsBase<Derived> is declared a friend class of Derived. To make the insertion operator available a private member

    void Derived::insert(std::ostream &out) const


        

    void Derived::extract(std::istream &in)


        

INHERITS FROM

--

OVERLOADED OPERATORS

For each defined Derived &&operator@=(Rhs const &rhs) &&, defined in the class Derived the following operators are automatically also available:

    Derived operator@(Derived &&lhs, Rhs const &rhs);


    Derived operator@(Derived const &lhs, Rhs const &rhs);


        

and

    Derived &operator@=(Rhs const &rhs) &;


        

The insertion operator becomew available once

    void Derived::insert(std::ostream &out) const


        

    void Derived::extract(std::istream &in)


        

FRIEND DECLARATION

To make the insertion and/or extraction operators available the class Derived must also declare

    friend FBB::BinopsBase<Derived>;


        

EXAMPLE

#include <iostream>
#include <bobcat/binopsbase>
class Demo1: public FBB::BinopsBase<Demo1>
{


    friend FBB::BinopsBase<Demo1>;            // for insert/extract


    public:


        void swap(Demo1 &other)


        {}


        Demo1 &&operator+=(Demo1 const &rhs) &&


        {


            std::cout << "adding two Demo1 objects\n";


            return std::move(*this);


        }
//  Explicit definitions take precedence over functions templates
//  instantiated from definitions in bobcat/binopsbase. 
//        Demo1 &operator+=(Demo1 const &rhs) &
//        {
//            std::cout << "adding (self-defined) two Demo1 objects\n";
//            return *this;
//        }


        Demo1 &&operator-=(Demo1 const &rhs) &&


        {


            std::cout << "subtracting two Demo1 objects\n";


            return std::move(*this);


        }


        Demo1 &&operator<<=(Demo1 const &rhs) &&


        {


            std::cout << "shiftleft on two Demo1 objects\n";


            return std::move(*this);


        }


        Demo1 &&operator<<=(size_t rhs) &&


        {


            std::cout << "shiftleft Demo1 object size_t bits\n";


            return std::move(*this);


        }


        void insert(std::ostream &out) const        // requires friend


        {


            out << "inerting a Demo1 object\n";


        }


        void extract(std::istream &in)              // requires friend


        {


            std::cout << "extracting a Demo1 object\n";


        }
};
class Demo2: public FBB::BinopsBase<Demo2>
{


    public:


        void swap(Demo2 &other)


        {}


        Demo2 &&operator+=(Demo2 const &rhs) &&


        {


            std::cout << "adding two Demo2 objects\n";


            return std::move(*this);


        }


        Demo2 &operator+=(Demo2 const &rhs) &


        {


            std::cout << "adding (self-defined) two Demo2 objects";


            return *this;


        }


        Demo2 &&operator^=(Demo2 const &rhs) &&


        {


            std::cout << "xor-ing two Demo2 objects\n";


            return std::move(*this);


        }


        Demo2 &&operator|=(Demo2 const &rhs) &&


        {


            std::cout << "or-ing two Demo2 objects\n";


            return std::move(*this);


        }
};
int main()
{


    Demo1 d1a, d1b;


    Demo1 d1c = d1a + d1b;


    d1a += d1b;


    d1c = Demo1{} + d1b;


    std::cout << "Here we are " << d1c << ’\n’;


    std::cin >> d1c;


    d1a <<= d1a;


    d1a <<= 5;


    Demo2 d2a, d2b;


    Demo2 d2c = d2a + d2b;


    d2a ^= d2b;


    d2c = Demo2{} ^ d2b;


    d2c = d2c | d2b;
}

FILES

bobcat/binopsbase - defines the binary operator function templates

SEE ALSO

bobcat/binops(3), bobcat(7)