passing a function pointer

Hello again!

I'm working on a project where I need a function to take the address of another function as its argument, then in the function I set a pointer to the address, like here:

Code:

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virtual void SetFrameFunc( bool &FrameFunc_() ) { pFrameFunc = &FrameFunc_(); }

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This doesn't give me an error, still I don't know how to use pFrameFunc now... Also, I want to do recursion to the function which address was passed to SetFrameFunc, does anyone have any ideas on how to do this?

Thanks in advance!

You call a function by placing the arguments in parentheses immediately following the name of the function, as

Code:

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pFrameFunc()

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since your function doesn't appear to take any arguments. I hope you intend the function to return a bool by reference, since that appears to be what you've got.

I have no idea what you think you mean by "recursion to the function which address was passed to SetFrameFunc". If the function passed in was written recursively, then there's nothing you need to do; if the function wasn't, there's nothing you can do. (Presumably both you and the person who wrote the function agree on what the function is supposed to accomplish; as long as it does so, then you don't care how.) If you mean you want to call it a bunch of times, then by all means call it a bunch of times.

I want to call it 'til the program shutdowns xP

EDIT: Also, it still doesn't work... How do I declare the pointer? My current way is...

Code:

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bool* pFrameFunc;

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Quote:

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Originally Posted by Akkernight

I want to call it 'til the program shutdowns xP

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Okay, but that's not recursion, that's a loop.

Doesn't a function pointer look more like?

Code:

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bool (*FrameFunc)()

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http://codepad.org/GQQgZhP0

There is the code, used codepad 'cause it's easier, now I tried your suggestion anon, still couldn't get it to work :S

So, you didn't define pFrameFunc to be a function pointer, hence your attempt to make it one will fail miserably. If you want it to be one, define it as such on line 7.

I've tried, but then I get invalid use of member message for the pFrameFunc = &FrameFunc thing...
That also depends on if function pointers are declared like bool* pFrameFunc(); ?

You probably need to look what's before LIQUID.

But the thing is,

Code:

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bool* x;

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This is a pointer to a bool.

Code:

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bool (*x)();

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This should be a pointer to a function that takes no arguments and returns bool.

Things might be more fishy if what you are trying to pass it is a member function.

Again, tried that...
I guess the problem lies in

Code:

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virtual void SetFrameFunc( bool &FrameFunc_() ) { pFrameFunc = &FrameFunc_(); }

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Code:

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//function pointers have a .......... of a syntax, so typedef them
typedef bool (*FrameFunction)();

class LIQUID {
private:

    SCREEN Screen;

    FrameFunction pFrameFunc;


public:

    LIQUID( bool& failed , const SCREEN Screen_ );
    ~LIQUID();

    virtual void SetFrameFunc( FrameFunction FrameFunc_ ) { pFrameFunc = FrameFunc_; }

};

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Something like this.

Awesome, it works! Thanks! :D
Now, how do I release this pointer? delete says it can't delete functions...

ok, now, how do I declare the prototype? :S

You don't release function pointers.

And what prototype do you mean?

The usage is supposed to be:

Code:

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bool SomeFunction()
{
    //...
    return something;
}

int main()
{
    //...
    LIQUID liquid(somebool, somescreen);
    liquid.SetFrameFunc(&SomeFunction);
    //...
}

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Quote:

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Originally Posted by Akkernight

ok, now, how do I declare the prototype? :S

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The prototype of what? You can't give a prototype of SetFrameFunc, since it's defined right there.

woops! Ain't thinking clear, sorry for that!
But thanks again, both of you! :D

http://codepad.org/opw4HeWp

Now, I'd like suggestions on this and is there anyway to check if a pointer, like the used pFrameFunc pointer, has been assigned anything else than 'garbage' ? Like, if it has been assigned by the code, and not some default compiler thing...

And for the suggestions, I mean would this be the right place for the loop? I don't want the users of this engine to make the loop themselves...
And I use the variable "bool& failed" as the condition for the loop, there is no problem with this? I mean, it is a pointer... Just to make me more sure about this!
Thanks in advance!

Quote:

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Now, I'd like suggestions on this and is there anyway to check if a pointer, like the used pFrameFunc pointer, has been assigned anything else than 'garbage' ? Like, if it has been assigned by the code, and not some default compiler thing...

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Like any other pointer you should set it to NULL initially, since NULL checks are the only way to make sure if the pointer points to something.

Quote:

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And for the suggestions, I mean would this be the right place for the loop? I don't want the users of this engine to make the loop themselves...
And I use the variable "bool& failed" as the condition for the loop, there is no problem with this? I mean, it is a pointer... Just to make me more sure about this!
Thanks in advance!

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I don't see why you'd want an infinite loop there.