std::bind to std::function?

Question

I get a compile error using this:

std::vector<std::function<int(int)>> functions;

std::function<int(int, int)> foo = [](int a, int b){ return a + b; };
std::function<int(int)> bar = std::bind(foo, 2);

functions.push_back(bar);

The error is:

/usr/include/c++/4.6/functional:1764:40: error: no match for call to '(std::_Bind(int)>) (int)'

Can someone tell me how to convert a std::bind into a std::function?

Solution

std::function<int(int)> bar = std::bind(foo, 2, std::placeholders::_1);

Comments

[BlackMamba]

` std::bind(foo, 2, std::placeholders::_1)` is equal to ` std::bind(foo, 2,)` ?

[Caleth]

@BlackMamba I think you are getting confused about which function has 2 parameters. A placeholder other than _1 implies the bind result has more than 1 parameter

[Francis Cugler]

This is the second Q/A I've came across this week that where the provided answer had used std::placeholders::... and before this week I was not familiar with it. It's always good to learn something new.