Question

In javascript it’s possible to do things like this:

SomeObject.somefunction(function(someparameters){
//do some things.
});

like in jquery each function:

$('.rawdata').each(function(index){
$(this).attr('some',index);
});

I searched and saw that in c/c++ we can use functions as parameters using function pointers, but didn’t found a way to do some thing like the above one: to declare the function that will be pointed in the moment that it will be used. So is this possible? If it isn’t, what would you recommend to use instead?

Answer 1

Check out lambda functions, added to C++ in the latest standard (C++11).

std::vector<int> vec;
// ...
// Double each element in the vector
std::transform(vec.begin(), vec.end(), [] (int elem) { return 2*elem; });

The parameter that will receive the function will have to be either a template (whose precise type will be automatically deducted from the lambda function itself), either std::function<> (a type-erasure class designed to hold any type of “callable thing” with the given prototype).

By the way, function pointers aren’t the only way to pass a function-like object to a procedure in C++ even before the C++11 standard: any object that overloads operator() (i.e. the function call operator) can be called as a function, and is said to be a “functor”. Functors are quite ubiquitous when programming with the STL¹ algorithms.

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1. @nitpickers: I know and I don’t care, we all know what I’m talking about.