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
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Why C++ standard library does not pass predicates as &&
In C++ stl, there is e.g.:
template
constexpr InputIt find_if( InputIt first, InputIt last, UnaryPredicate p );
My question is: why there is not:
... find_if(..., UnaryPredicate &&p);
In my understanding it…
Jarek C
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1 answer
How can I compare std::function objects?
I have a vector of std::function objects defined like this:
std::vector> funcs = { myFunc1, myFunc2, myFunc3 };
//The functions are defined like this:
//void myFunc1() { ... }
I am trying to search through this array for a…
DarkAtom
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0 answers
Retrieve parameter types of all overloads of callable operators of function object
#include
#include
struct foo
{
void operator()( const int& ) { }
void operator()( const float& ) { }
void operator()( const std::string& ) { }
};
template
void bar_recursive()
{
std::cout <<…
calynr
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1
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2 answers
for_each weird behaviour
I don't use the STL much and I'm wanting to start learning it, so I made a really simple program using the STL's for_each function. Here is the entire program (minus header files):
class Object {
public:
int s;
Object() : s(0) { }
…
Seth Carnegie
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1
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2 answers
Omitting type parameter for greater template in C++ STL
Here is a line of code I read in a book
priority_queue, greater<>> min_heap;
where IteratorCurrentAndEnd is a class implementing a operator> method. Why can we have greater<> instead of…
Sean
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1
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1 answer
Is it wise to prefer lambdas to function objects?
After some searching and testing, I have learned the following facts about lambda expression. 1) when we write a lambda expression, the compiler would create an anonymous function object for it, and make it as an instance of the function object; 2)…
Kenan Si
- 13
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1
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2 answers
Possible to pass a function into a object's method as an argument, which can refer to that object?
def my_func():
stuff
return something
my_object.my_method(my_func)
I want my_func to be able to refer to my_object. Essentially like deferred self, which means "whatever object I am in, refer to that"
Jonny Shanahan
- 351
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1
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1 answer
Terminology surrounding functors
Let's take a simple functor
class LessThan {
public:
explicit LessThan (int in ) : val(in) {}
bool operator() (int param) const {
return param < val;
}
private:
int val;
};
which I can use like this for example -…
The Vivandiere
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1
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2 answers
parsing JSON - eval() or function object?
To parse JSON, I believe the best method is to use native JSON support in browsers.
I was looking for a good way to parse JSON in cases where native JSON support is not available.
When i looked at the code in…
Anish
- 1,164
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1
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0 answers
c++: how to pass pointer and functor as template arguments
I want to pass class pointer and a functor as a class template argument.
I also dont want that that class pointer to be a local member of functor.
I want to use an existing template class which is used elsewhere in the code, so I want to apply a…
bsobaid
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1
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1 answer
Function object as template parameter
template >
class LessThanPred {
public:
LessThanPred(const elemType &val) : _val(val){}
bool operator()(const elemType &val) const
{ return Comp(val, _val); }
…
yycfox
- 13
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1
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1 answer
cout printing in reverse order
Trying overloading operator() in the following example:
#include
using namespace std;
class Fib {
public:
Fib() : a0_(1), a1_(1) {}
int operator()();
private:
int a0_, a1_;
};
int Fib::operator()() {
int temp = a0_;
…
KKG10
- 11
- 2
1
vote
2 answers
Prefer function-pointer or function-object when customizing sort and map?
I want to customizing sort template and map template in C++
Here are for comparing,
struct Greater1
{
bool operator() (string A, string B)
{
string AB = A + B;
string BA = B + A;
return (AB >BA);
}
};
static bool…
Yutao Xing
- 41
- 5
1
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2 answers
Scala Trait and function object
I'm starting to learn Play,
and i'm stuck in trying to understand how Action is implemented. I just don't understand the language construct and that really frustrate me.....
I don't understand how one can write ?
val echo = Action { request =>…
MaatDeamon
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1
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1 answer
Which comes first, Function or Object?
There's this Object Layout diagram nicely explains the prototype chain in javascript. But it's a bit confusing to me when it comes to the relationships between the followings:
function Object(){}
Object.prototype
function…
Aaron Shen
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