In object-oriented languages, function object (also known as functor) is a feature that allows objects to be used like if they were ordinary functions.
Questions tagged [function-object]
168 questions
12
votes
2 answers
How do function objects affect overload resolution?
Are function objects treated differently from regular functions during overload resolution? If so, how?
I have run into the following case where replacing a function with an equivalently-callable function object changed the meaning of the…
HighCommander4
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votes
4 answers
STL Functional -- Why?
In C++ Standard Template Library, there's a 'functional' part, in which many classes have overloaded their () operator.
Does it bring any convenience to use functions as objects in C++?
Why can't we just use function pointer instead? Any examples?
Determinant
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11
votes
3 answers
Are function pointers function objects in C++?
The C++ standard defines function objects as:
A function object type is an object type that can be the type of the
postfix-expression in a function call. (link)
First I was thinking that function objects were functors, but then I realized that…
Vincent
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6 answers
When do you use function objects in C++?
I see function objects used often together with STL algorithms. Did function objects came about because of these algorithms? When do you use a function object in C++? What is its benefits?
jasonline
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10
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function objects versus function pointers
I have two questions related to function objects and function pointers,
Question : 1
When I read the different uses sort algorithm of STL, I see that the third parameter can be a function objects, below is an example
class State {
public: …
kumar_m_kiran
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9
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C++ equivalent of C#'s Func
The following code computes the average of a particular property of T in the items collection:
public double Average(IList items, Func selector)
{
double average = 0.0;
for (int i = 0; i < items.Count; i++)
{
…
aligray
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9
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3 answers
How to document a function object with doxygen?
How should I document a function object (AKA functor) with doxygen? It feels misleading to just document it as a regular class. I find it much better to think of a function object as a function with a closure than a callable class.
Is there a way…
deft_code
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9
votes
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Functors: templated struct vs templated operator()
The usual pattern for standard library function objects is to have a templated struct with a non-template operator(). For example, std::less looks something like so:
template
struct less
{
bool operator()(const T& lhs, const T& rhs)…
Tristan Brindle
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9
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2 answers
Const and non-const functors
This seems like something that ought to be frequently asked and answered, but my search-fu has failed me.
I'm writing a function which I want to accept a generic callable object of some kind (including bare function, hand-rolled functor object,…
Miral
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8
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What's the meaning of &T::operator() in function traits?
// Fallback, anything with an operator()
template
struct function_traits : public function_traits > {
};
What does T::operator() mean here?
This is code from pytorch.
ben19900305
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8
votes
2 answers
Detecting function object (functor) and lambda traits
How can I detect the return type and parameter types of nullary and unary function pointers, std::function objects, and functors (including lambdas)?
Boost's function_traits and functional traits don't quite get me there out of the box, but I'm open…
metal
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8
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5 answers
how to pass a class method as argument to another method of the class in perl 6
I have a script like the below. Intent is to have different filter methods to filter a list.
Here is the code.
2
3 class list_filter {
4 has @.my_list = (1..20);
5
6 method filter($l) { return True; }
7
8 # filter method
9 …
BhaskarS
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8
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2 answers
What is the correct argument type for a function-object?
I have a templated function that receives function-objects. Sometimes the function-objects are stateless structs, but sometimes they are large statefull objects. The state of the function-object is not changed in this function, only examined. I'm…
Mankka
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6 answers
Recursively call a function object
How do I call a function object from within itself? Seems I cannot use this. Example:
class factorial {
public:
int operator()(int n) {
if (n == 0)
return 1;
return n * ??(n-1);
}
};
What do I place at ???
r.v
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Why can C++ functors be preferable to objects with named methods?
I recently have got excited by functors and been using them all over the place. Then the situation arose where I needed my functor to perform two different operations and I thought about adding another method to my functor (not overloading the ()…
zenna
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