Comments on: 7.8 — Function Pointers

By: Alex

Alex — Thu, 24 Jul 2008 01:33:49 +0000

Oops, how did I miss Stuart’s original comments? In any case, I think it should be fixed now.

Thanks for catching this.

By: Sean

Sean — Wed, 23 Jul 2008 15:19:27 +0000

I agree with Simon: the comments should be exchanged.

By: Simon

Simon — Mon, 14 Jul 2008 08:50:00 +0000

bool EvensFirst(int nX, int nY)

Alex your comments are incorrect in this function as pointed out by Stuart.

You can either change the if statements to match the comments or change the comments to match the statements.

You need to change the 1st comment with the second, and vice versa .
Stuart’s changes also correct the anomalies.

Regards
Simon

By: Stuart

Stuart — Fri, 30 May 2008 17:41:03 +0000

I get it now, after rewriting the EvensFirst function to this:

bool EvensFirst(int nX, int nY)
{
	// if nX is even and nY is not, nX goes first
	if ((nX % 2 == 0) && !(nY % 2) == 0)
		return true;

	// if nX is not even and nY is, nY goes first
	if (!(nX % 2 == 0) && (nY % 2 == 0))
		return false;

	// otherwise sort in Ascending order
	return Ascending(nX, nY);
}

I got mixed up and didn’t realize that nX % 2 actually means that nX is NOT divisible by 2 and !nX % 2 means that it IS divisible by 2.

By: Stuart

Stuart — Thu, 29 May 2008 15:57:55 +0000

bool EvensFirst(int nX, int nY)   
{   
        // if nX is even and nY is not, nX goes first   
    if ((nX % 2) && !(nY % 2))   
        return false;   
  
        // if nX is not even and nY is, nY goes first   
    if (!(nX % 2) && (nY % 2))   
        return true;   
  
        // otherwise sort in Ascending order   
    return Ascending(nX, nY);   
}

How is bool working here? How is the return false and return true working to return the integers in different orders?

By: Learn C++ - » 7.7 — Default parameters

Learn C++ - » 7.7 — Default parameters — Tue, 29 Apr 2008 05:04:38 +0000

[...] 2007 Prev/Next Posts « 7.6 — Function overloading | Home | 7.8 — Function Pointers » Monday, August 6th, 2007 at 4:38 [...]

By: shyan

shyan — Mon, 24 Mar 2008 06:34:22 +0000

typedef of function pointer looks complex.
no typedef variable. how it assumed that pfcnVlidate is typedef… confuse

shyam

By: Alex

Alex — Mon, 14 Jan 2008 15:56:08 +0000

This is one of the really ugly parts of C++. Basically, the type is a pointer to a function returning a bool and taking 2 int parameters, and the name of the typedef is pfcnValidate.

I suspect they did the syntax this way to mimic the way actual function declarations look, but I agree that it doesn’t map to the typedef syntax in a very intuitive manner. It’s one of those things I have to look up how to do every time I need to do it… but that’s still better than not using typedefs at all.

By: Renu

Renu — Mon, 14 Jan 2008 04:29:53 +0000

Syntax of typedef is:
typedef type alias name;

How does that map to:
typedef bool (*pfcnValidate)(int, int);

This seems complex.

Renu

By: Ainsley

Ainsley — Sun, 19 Aug 2007 01:12:52 +0000

hi i enjoyed the read