Problem: passing function as argument !!!

Sebastiani · 07-16-2009, 02:11 PM

>> That's why there are two overloads! One for const, one for non-const.

What, you expect me to actually read the code?

>> I'm just concerned about returning void from the FncPtr call.

Code:

template < typename R >
R foo( R ( *f )( ) )
{
	return f( );
}

int bar( void )
{
	return 3114;
}

void qux( void )
{	}

int main( void )
{
	cout << foo( bar ) << endl;
	foo( qux );
	return 0;
}

Elysia · 07-16-2009, 02:26 PM

Quote:

Originally Posted by Sebastiani

>> That's why there are two overloads! One for const, one for non-const.
What, you expect me to actually read the code?

Aww, come on. It's not that big and complicated.
So this actually compiles, where you try to return "void"?

Sebastiani · 07-16-2009, 02:32 PM

>> Aww, come on. It's not that big and complicated.

Oh I know, I should have paid closer attention.

>> So this actually compiles, where you try to return "void"?

Yep. As long as you don't try to explicitly declare a variable of that type, though (which is really too bad because that would have been a useful feature). So in other words, this would not compile if used with void:

Code:

template < typename R >
R foo( R ( *f )( ) )
{
	R r = f( );		
	return r;
}

Elysia · 07-16-2009, 02:34 PM

Alright, cool, no worries about that then.

tharnier · 07-16-2009, 02:40 PM

Quote:

Originally Posted by Elysia

Two examples.
One using boost, the other without boost.

Code:

class ExClass 
{
public:
    int func(const int& z); //***
};

int ExClass::func(const int& z) { return z; }

template <typename T>
void example(T& func) { func(); }

template <typename Class_t, typename Fnc_t>
void example2(Class_t& Class, Fnc_t FncPtr) { (Class.*FncPtr)(); }

int main()
{
     ExClass f;
     example( boost::bind(&ExClass::func, f) );
     example2(f, &ExClass::func);
     return 0;
}

And don't forget to read this:
https://apps.sourceforge.net/mediawi...arameter_names

I cant read this because its looked...

And, I cant see but when I am compiling that, its returning a error:

Code:

 In function ‘void example2(Class_t&, Fnc_t) [with Class_t = ExClass, Fnc_t = int (ExClass::*)(const int&)]’:
16:   instantiated from here
10: error: too few arguments to function

What is wrong?

Elysia · 07-16-2009, 02:49 PM

Ah, that's because the function takes an int, but we don't pass one. You can fix it like:
(Class.*FncPtr)(10);
func(10);

tharnier · 07-16-2009, 02:53 PM

Quote:

Originally Posted by Elysia

Ah, that's because the function takes an int, but we don't pass one. You can fix it like:
(Class.*FncPtr)(10);
func(10);

hmmmm that is what I was trying to avoid...
But I'm trying to use boost::function...

Do you know some really good book to indicate to me??? with this kind of doubt

Elysia · 07-16-2009, 02:58 PM

Oh? Then let's borrow the power of boost::bind a little more:
example( boost::bind(&ExClass::func, f, 10) );
Notice that I put a number in there as well.
Now
func();
Simply will work.
Praised be boost!

tharnier · 07-16-2009, 03:08 PM

What probably will solve my problem is:

Code:

ExClass f;
f.func = boost::bind( &ExClass::func, &f );
example( f.func );

isn't?

But, do I really need to install all boost library to use boost::bind()???

Elysia · 07-16-2009, 03:11 PM

It doesn't work that way! Just pass what boost::bind returns directly to your function.
You need to download the boost package, yes, but you don't need to install any dlls to use it. However, you can't just break it into pieces since it has dependencies on other headers in the boost distribution.

Code:

ExClass f;
example( boost::bind(&ExClass::func, f, 1000) );

tharnier · 07-16-2009, 03:14 PM

Quote:

Originally Posted by Elysia

It doesn't work that way! Just pass what boost::bind returns directly to your function.
You need to download the boost package, yes, but you don't need to install any dlls to use it. However, you can't just break it into pieces since it has dependencies on other headers in the boost distribution.

Code:

ExClass f;
example( boost::bind(&ExClass::func, f, 1000) );

Ok, and how about the book???
Can you suggest one??
To look up that kind of doubt?

Elysia · 07-16-2009, 03:17 PM

Not much about boost, sadly.
There is one book about boost, I think. Can't remember its name. It's somewhat old and doesn't cover that much, but it's about the only one available or so. A search on the web should reveal more information about that.
Otherwise the boost homepage is your best source of information.

tharnier · 07-16-2009, 03:20 PM

Quote:

Originally Posted by Elysia

Not much about boost, sadly.
There is one book about boost, I think. Can't remember its name. It's somewhat old and doesn't cover that much, but it's about the only one available or so. A search on the web should reveal more information about that.
Otherwise the boost homepage is your best source of information.

No no, not about boost... about c++, but not too beginer, I say intermediate!!!!

Elysia · 07-16-2009, 03:23 PM

Oh, okay. Then check the books thread.
If you haven't checked out Accelerated C++, then you should probably do that too.
It doesn't cover just the basics; it covers a lot of more and a lot of it is handy stuff!

tharnier · 07-16-2009, 03:25 PM

Quote:

Originally Posted by Elysia

Oh, okay. Then check the books thread.
If you haven't checked out Accelerated C++, then you should probably do that too.
It doesn't cover just the basics; it covers a lot of more and a lot of it is handy stuff!

Ok, thank you all your attention and patient to my problem!!!!

07-16-2009, 02:11 PM	#16
Sebastiani Guest Join Date: Aug 2001 Posts: 4,923	>> That's why there are two overloads! One for const, one for non-const. What, you expect me to actually read the code? >> I'm just concerned about returning void from the FncPtr call. Code: template < typename R > R foo( R ( *f )( ) ) { return f( ); } int bar( void ) { return 3114; } void qux( void ) { } int main( void ) { cout << foo( bar ) << endl; foo( qux ); return 0; }
Sebastiani is offline

07-16-2009, 02:32 PM	#18
Sebastiani Guest Join Date: Aug 2001 Posts: 4,923	>> Aww, come on. It's not that big and complicated. Oh I know, I should have paid closer attention. >> So this actually compiles, where you try to return "void"? Yep. As long as you don't try to explicitly declare a variable of that type, though (which is really too bad because that would have been a useful feature). So in other words, this would not compile if used with void: Code: template < typename R > R foo( R ( *f )( ) ) { R r = f( ); return r; }
Sebastiani is offline

07-16-2009, 03:08 PM	#24
tharnier Registered User Join Date: Jul 2009 Posts: 11	What probably will solve my problem is: Code: ExClass f; f.func = boost::bind( &ExClass::func, &f ); example( f.func ); isn't? But, do I really need to install all boost library to use boost::bind()???
tharnier is offline

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Passing A Function Into A Constructor	fourplay	C++ Programming	6	03-15-2009 06:06 AM
Compiling sample DarkGDK Program	Phyxashun	Game Programming	6	01-27-2009 03:07 AM
Passing function as argument	NeMewSys	C Programming	16	06-11-2008 02:03 PM
passing a function as an argument	angelscars	C++ Programming	6	12-06-2005 09:53 PM
Didn't quite know where to post this.......compiler problem...	incognito	C++ Programming	5	02-08-2003 07:42 PM