Callable object
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A callable object, in computer programming, is any object that can be called like a function.
In different languages
In C++
- pointer to function;
- pointer to member function;
- functor;
- lambda expression.
std::functionis a template class that can hold any callable object that matches its signature.
In C++, any class that overloads the function call operator operator() may be called using function-call syntax.
In C#
- delegate;
- lambda expression.
In PHP
PHP 5.3+ has first-class functions that can be used e.g. as parameter to the usort() function:
It is also possible in PHP 5.3+ to make objects invokable by adding a magic __invoke() method to their class:
In Python
In Python any object with a __call__() method can be called using function-call syntax.
Another example:
In Dart
Callable objects are defined in Dart using the call() method.
In Swift
In Swift, callable objects are defined using callAsFunction.