I cannot find out how to bind a parameter to an overloaded function using std::bind
. Somehow std::bind
cannot deduce the overloaded type (for its template parameters). If I do not overload the function everything works. Code below:
#include <iostream>
#include <functional>
#include <cmath>
using namespace std;
using namespace std::placeholders;
double f(double x)
{
return x;
}
// std::bind works if this overloaded is commented out
float f(float x)
{
return x;
}
// want to bind to `f(2)`, for the double(double) version
int main()
{
// none of the lines below compile:
// auto f_binder = std::bind(f, static_cast<double>(2));
// auto f_binder = bind((std::function<double(double)>)f, \
// static_cast<double>(2));
// auto f_binder = bind<std::function<double(double)>>(f, \
// static_cast<double>(2));
// auto f_binder = bind<std::function<double(double)>>\
// ((std::function<double(double)>)f,\
// static_cast<double>(2));
// cout << f_binder() << endl; // should output 2
}
My understanding is that std::bind
cannot deduce somehow its template parameters, since f
is overloaded, but I cannot figure out how to specify them. I tried 4 possible ways in the code (commented lines), none works. How can I specify the type of function for std::bind
? Any help is much appreciated!
You may use:
auto f_binder = std::bind(static_cast<double(&)(double)>(f), 2.);
or
auto f_binder = bind<double(double)>(f, 2.);
Alternatively, lambda can be used:
auto f_binder = []() {
return f(2.); // overload `double f(double)` is chosen as 2. is a double.
};