Recursive function inside of a function c++

Question

Say I have a wrapper function that goes around some smaller recursive function. However, the wrapper, before calling the recursive function creates an object which the recursive function uses. How can I do this in c++? Do I just need to make it its own class? EDIT - I know if I can make it into a class and how to take it from there - but my question is do I need a class or can I somehow getaway without making one?

I made a generic example to clarify my question:

void wrapper()
{
    Object myObject;
    bool recurFun(int x)
    {
        // do some stuff with myObject
        if (some condition){return recurFun(x-1)}
        else {return true}
    }
}

Please ignore any basic syntax type errors, it is not a working example simply one to help get my question across to you guys. Thanks!

If the code you provided works, where is your problem? If the code you provided does not work, in what way does it behave differently than you intended? — Oswald, Apr 26 '13 at 23:52
I know I could make it work if I made a class, but I really don't want to if there is a simpler way to do (without a class). — Joker, Apr 26 '13 at 23:55

score 14 · Accepted Answer · answered Apr 26 '13 at 23:56

14

You can use lambdas to get closures:

void wrapper()
{
    Object myObject;
    std::function<bool(int)> recurFun;
    recurFun = [&](int x) -> bool {
        // do some stuff with myObject
        if (some condition){return recurFun(x-1)}
        else {return true}
    }
}

answered Apr 26 '13 at 23:56

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Looks like you have beaten me to this answer :) – Swiss Apr 26 '13 at 23:58
It would be nice if SO allows favor an answer. – StarPinkER Apr 27 '13 at 00:07
Wonderful - exactly what I was looking for. – Joker Apr 27 '13 at 01:12

score 2 · Answer 2 · answered Apr 27 '13 at 00:01

The first thing that should come to your mind when a function needs to use something is to make it a parameter of that function. So have your recursive function accept the object as a parameter and thread it around in the recursive calls. The wrapper function will do the natural thing of setting up the object and passing it.

Recursive function inside of a function c++

2 Answers2