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For example, the use of the << operator in C++ a << b shifts the bits in the variable a left by b bits if a and b are of an integer type, but if a is an output stream then the above code will attempt to write a b to the stream.
// A class template to express an equality comparison interface. template < typename T > class equal_comparable {friend bool operator == (T const & a, T const & b) {return a. equal_to (b);} friend bool operator!= (T const & a, T const & b) {return! a. equal_to (b);}}; // Class value_type wants to have == and !=, so it derives from // equal_comparable with itself as argument (which is the CRTP ...
This is an example of overloading or more specifically, operator overloading. Note the ambiguity in the string types used in the last case. Consider "123" + "456" in which the programmer might naturally assume addition rather than concatenation. They may expect "579" instead of "123456". Overloading can therefore provide different meaning, or ...
Bjarne Stroustrup, the creator of C++, wrote the first version of the stream I/O library in 1984, as a type-safe and extensible alternative to C's I/O library. [5] The library has undergone a number of enhancements since this early version, including the introduction of manipulators to control formatting, and templatization to allow its use with character types other than char.
All logical operators exist in C and C++ and can be overloaded in C++, albeit the overloading of the logical AND and logical OR is discouraged, because as overloaded operators they behave as ordinary function calls, which means that both of their operands are evaluated, so they lose their well-used and expected short-circuit evaluation property ...
In languages that support operator overloading by the programmer (such as C++) but have a limited set of operators, operator overloading is often used to define customized uses for operators. In the example IF ORDER_DATE > "12/31/2011" AND ORDER_DATE < "01/01/2013" THEN CONTINUE ELSE STOP, the operators are: > (greater than), AND and < (less than).
For example, to have a derived class with an overloaded function taking a double or an int, using the function taking an int from the base class, in C++, one would write: class B { public : void F ( int i ); }; class D : public B { public : using B :: F ; void F ( double d ); };
Figure 5: Example of how operator overloading could work. Operator overloading is a possibility for source code written in a language supporting it. Objects for real numbers and elementary mathematical operations must be overloaded to cater for the augmented arithmetic depicted above.