In C++, function call operator is a construct that allows object to be used like it were a function. This feature in general is known as function object (functor).
Questions tagged [function-call-operator]
20 questions
1061
votes
14 answers
What are C++ functors and their uses?
I keep hearing a lot about functors in C++. Can someone give me an overview as to what they are and in what cases they would be useful?
Konrad
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82
votes
12 answers
Why override operator()?
In the Boost Signals library, they are overloading the () operator.
Is this a convention in C++? For callbacks, etc.?
I have seen this in code of a co-worker (who happens to be a big Boost fan). Of all the Boost goodness out there, this has only led…
JeffV
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24
votes
3 answers
Why is a lambda's call-operator implicitly const?
I have a small "lambda expression" in the below function:
int main()
{
int x = 10;
auto lambda = [=] () { return x + 3; };
}
Below is the "anonymous closure class" generated for the above lambda expression.
int main()
{
int x = 10;
…
cpp_enthusiast
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16
votes
2 answers
In a function call, what is the operator, and what are the operands?
I am trying to understand some basics of C. KRC's The C Programming Language says
A function call is a postfix expression, called the function designator, followed by parentheses containing a possibly empty, comma-separated list of …
Tim
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11
votes
4 answers
How do I implement the Fn trait for one struct for different types of arguments?
I have a simple classifier:
struct Clf {
x: f64,
}
The classifier returns 0 if the observed value is smaller than x and 1 if bigger than x.
I want to implement the call operator for this classifier. However, the function should be able to take…
asdetrefle
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7
votes
2 answers
Function call operator
Possible Duplicates:
C++ Functors - and their uses.
Why override operator() ?
I've seen the use of operator() on STL containers but what is it and when do you use it?
george
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4
votes
1 answer
Passing a static operator() as deleter type
Is the following code snippet legal in C++23?
#include
#include
int main()
{
struct custom_deleter
{
static void operator()(int* const ptr)
{
delete ptr;
std::fputs( "Deleted\n",…
digito_evo
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3
votes
4 answers
What does void Classname::operator()(){ .... } do?
Im working my way through some C++ code and came across the following
void Classname::operator()()
{
//other code here
}
I assume this has something to do with overloading the constructor, but can someone elaborate on that?
madmaze
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2
votes
2 answers
overload assignment and round bracket operator in C++
I want to define a class myVector that support both assignment operator= and bracket access e.g myclass(1) = 0.5. See a dummy example below
class myVector
{
public:
vector _v;
myVector(unsigned int size) : _v(size, 0) { }
…
Peter Trade
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2
votes
1 answer
Is there a way to spawn a std::thread using an object and its non-empty argument list call operator?
I'm new to std::thread and C++11 in general. Trying to toy with the examples from https://en.cppreference.com/w/cpp/thread/thread/thread, I am trying to see if I can spawn a std::thread using a class member function call operator with non-empty…
StoneThrow
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2
votes
2 answers
How to Implicitly Call a Function Call Operator?
How does one implicitly call a class object's templated function call operator?
class User_Type
{
public:
template< typename T > T operator()() const;
};
void function()
{
User_Type user_var;
int int_var_0 = user_var.operator()< int…
Charles L Wilcox
- 1,126
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2
votes
2 answers
Overload function-call operator and return type
I'm designing a little mathematical library. I have classes that represents classes of function, e.g. polynomial. When they're instantiated, the parameters needed (a1, a2, a3) are provided so the object actually represent a specific polynomial…
LordM'zn
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- 4
1
vote
2 answers
Passing a reference to template function call operator overload
I have a class which overloads the function call operator with a template function, like so:
class Test
{
public:
template
void operator()(T t)
{
std::cout<<(&t)<
Silverlan
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1
vote
1 answer
C++ - Template function call operator overload - Error C2064
I'm trying to overload function call operator in c++ and I got this compilation error that I cannot resolve (Visual Studio 2010).
Error is in line act(4);
#include
#include
void Test(int i);
template class Action
{
…
EOG
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0
votes
0 answers
How to overload the function call operator based on whether called from the left-hand or right-hand side
Is it possible to const-overload the function call operator operator() so that:
when the caller is on the left-hand side of an expression, the non-constant version is always called
when the caller is on the right-hand side of the expression, the…
Petri Hirvonen
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- 6