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The functions must have different type signatures, i.e. differ in the number or the types of their formal parameters (as in C++) or additionally in their return type (as in Ada). [9] Function overloading is usually associated with statically-typed programming languages that enforce type checking in function calls. An overloaded function is a ...
The act of creating such alternative functions for compile time selection is usually referred to as overloading a function. In programming languages that defer data type identification until run time (i.e., late binding ), selection among alternative functions must occur then, based on the dynamically determined types of function arguments.
Often the compiler selects the overload to call based on the type of the input arguments or it fails if the input arguments do not select an overload. Older and weakly-typed languages generally do not support overloading. Here is an example of overloading in C++, two functions Area that accept different types:
The previous section notwithstanding, there are other ways in which ad hoc polymorphism can work out. Consider for example the Smalltalk language. In Smalltalk, the overloading is done at run time, as the methods ("function implementation") for each overloaded message ("overloaded function") are resolved when they are about to be executed.
The problem is that, while virtual functions are dispatched dynamically in C++, function overloading is done statically. The problem described above can be resolved by simulating double dispatch, for example by using a visitor pattern. Suppose the existing code is extended so that both SpaceShip and ApolloSpacecraft are given the function
If it does not work, the only available function is the second test, and the resulting type of the expression is no. An ellipsis is used not only because it will accept any argument, but also because its conversion rank is lowest, so a call to the first function will be preferred if it is possible; this removes ambiguity.
Virtual functions allow a program to call methods that don't necessarily even exist at the moment the code is compiled. [citation needed] In C++, virtual methods are declared by prepending the virtual keyword to the function's declaration in the base class. This modifier is inherited by all implementations of that method in derived classes ...
Operator overloading does not change the expressive power of a language (with functions), as it can be emulated using function calls. For example, consider variables a, b and c of some user-defined type, such as matrices: a + b * c