what is the use of a function pointer?

[northfly]

Under any circumstances I can think of, when I feel I need use a function pointer, I can always use some if and switch statement to replace.

Cannot think of any particular use of a function pointer!!!

[N36fSL3A]

You need them to dynamically load libraries at runtime. Your DLL/SO exports function names, and you load them into your program. From there you use them.

[TwilightSpectre]

There are also times when using function pointers (especially passing them to functions) is easier. For example, you could write a generic sort function, but rather than having it sort '<' all the time, you could make it take a function pointer of a compare. std::sort is like this, you can call it like so:

// sort based on the squares of numbers, in descending order
bool comp(int a, int b) {
    return a*a > b*b;
}

std::vector<int> myvec = {-5, 4, -2, 8, 1};
std::sort(myvec.begin(), myvec.end(), comp);

Also, function pointers can be used for lazy evaluation of functions.