C / C++ / MFC

Re: Converting char* to LPCSTR

5-Mar-10 14:27

I believe that LPCSTR is just const char *, so there is no conversion necessary. Just try:

LPCSTR p1 = param1;

Now, since p1 is a pointer to const, what it points to can not be changed through it.

Going the other way is an issue because what is being pointed to is presumably const, so you should not point a pointer-to-non-const to it. That would break the do not alter rule. So conversion isn't really the issue, but rather making an alterable copy of the original.

Now, if unicode was involved on one side but not the other, ... but that's not your question. Smile | :)

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ArnorBld8-Mar-10 7:33

ArnorBld

8-Mar-10 7:33

Thank you Avi for a very quick response. I think I have this under control now Smile | :)

Best regards,

Problem with one of the MFC new feature pack controls CMFCPropertyGridCtrl

A&Ms5-Mar-10 11:10

A&Ms

5-Mar-10 11:10

Hi,
How could I change the CMFCPropertyGridCtrl Property Column or Value column width?
a sample code would be more useful

c++ and using public static members in a class

Alan Kurlansky5-Mar-10 10:30

Alan Kurlansky

5-Mar-10 10:30

How do you do a extern type declaration for this. At link time I get unresolved external symbol "public: static void__cdecl etc. etc.
I'm trying to expand my use of C++ to envelop static functions inside of classes as a way to help organize the code a bit better.

Re: c++ and using public static members in a class

C^hris L^osinger5-Mar-10 10:57

5-Mar-10 10:57

this worked for me:

class A 
{
public:
    static void g(int)
    {
        int i = 0;
    }
};

typedef void (*fp)(int);

int _tmain(int argc, _TCHAR* argv[])
{
    fp p = A::g;
    p(1);
    return 0;
}

Re: c++ and using public static members in a class

Alain Rist5-Mar-10 11:08

Alain Rist

5-Mar-10 11:08

// MyClass.h
class MyClass
{
	static INT m_i;
	// ...
};
// if you want to keep it in definition part
__declspec(selectany) INT MyClass::m_i; // default initialized to 0

// MyClass.cpp
// ...
// if you want to have it in implementation part
INT MyClass::m_i; // default initialized to 0
// ...

cheers,
AR

When the wise person points at the moon the fool looks at the finger (Chinese proverb)

Re: c++ and using public static members in a class

Avi Berger5-Mar-10 12:52

Re: c++ and public static member functions - alternative approach

5-Mar-10 12:52

Static member functions usage:

MyClass.h:

class MyClass
{
public:
    static int fcn( int param );
    static int inlineFcn( int param) )    // may be inlined, but not guaranteed
    {
         // just a little stuff
    };
};

MyClass.cpp:

#include "Myclass.h"

int MyClass::fcn( int param )
{
    // stuff
}

Client.cpp:

#include "Myclass.h"

void clientFcn( int a, int b )
{
    // stuff

    int c = MyClass::fcn( a );
    int d = MyClass::inlineFcn( b );

    // more stuff
}

It sounds to me that another approach might be more suitable for your purposes. I'll post that next.

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Avi Berger5-Mar-10 13:26

Re: c++ and public static member functions - alternative approach

5-Mar-10 13:26

Alan Kurlansky wrote:
a way to help organize the code a bit better

It sounds to me like you want the organization, but what you are doing is not truly about classes and object orientation. There is another facility in C++, namespaces, that may be more appropriate for your current use. It organizes things in groups and helps avoid naming conflicts, but does not raise the "object" expectations of someone reading your code.

In some ways using namespaces looks a lot like what I posted for static member functions.

This is how you might use namespaces:

Group.h:

namespace Group
{
    int fcn( int param );
    inline int inlineFcn( int param) )    // may be inlined, but not guaranteed
    {
         // just a little stuff
    };
}

Group.cpp:

#include "Group.h"

namespace Group
{
    int fcn( int param )
    {
        // stuff
    }
}

Client.cpp:

#include "Group.h"

void clientFcn( int a, int b )
{
    // stuff

    int c = Group::fcn( a );
    int d = Group::inlineFcn( b );

    // more stuff
}

AlternateClient.cpp:

#include "Group.h"

using namespace Group;

void altClientFcn( int a, int b )
{
    // stuff

    int c = fcn( a );
    int d = inlineFcn( b );

    // more stuff
}

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Alan Kurlansky6-Mar-10 11:34

Alan Kurlansky

6-Mar-10 11:34

Yes, organization is what I'm looking to do in this case. This looks good. I'll give this a try. Thanks

Re: c++ and public static member functions - alternative approach

Avi Berger6-Mar-10 16:43

Re: c++ and public static member functions - alternative approach

6-Mar-10 16:43

Good luck. I hope it works well for you.

I will add a note about style. My example showed indenting a level inside the namespace definitions, just like you would do for any other pair of {}'s. There are style guidelines that recommend not doing so for namespaces. I'm undecided about this myself.

Please do not read this signature.

Alan Kurlansky6-Mar-10 11:35

Alan Kurlansky

6-Mar-10 11:35

Thanks. This looks good. I'll give it a try.

Bagh! Pointers

Herboren5-Mar-10 9:53

Herboren

5-Mar-10 9:53

I was reading http://www.cplusplus.com/doc/tutorial/pointers/
I understood most of what they were saying, so I chose to write my own code and comment what I have done to remember it in the future, but then its starts getting confusing near "Pointers and arrays" can anyone point out some simpler code for me to understand, so far this is the last thing I created::

// Pointers.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include < conio.h >
using namespace std;

int _tmain(int argc, _TCHAR* argv[])
{
	int fI = 3, sI = 2, tI = 1;
	int * p1, * p2, * p3;

	 p1 = &fI;			//Reference of first Integere held in p1
	 cout << p1 << ": ";
	*p1 = fI;			//*p1 points to the varible reference at location 
	cout << *p1 << endl;
	
	 p2 = &sI;			//Reference of second first Integere held in p2
	 cout << p2 << ": ";
	*p2 = sI;			//*p2 points to the varible reference at location 
	cout << *p2 << endl;

	 p3 = &tI;			//Reference of third Integere held in p3
	 cout << p3 << ": ";
	*p3 = tI;			//*p3 points to the varible reference at location 
	cout << *p3 << endl;

	_getch();
	return 0;
}

Re: Bagh! Pointers

C^hris L^osinger5-Mar-10 10:31

5-Mar-10 10:31

this tutorial[^] looks pretty good.

the "Decimal" data type in vc++

Re: Bagh! Pointers

David Crow5-Mar-10 10:48

David Crow

5-Mar-10 10:48

Herboren wrote:
...can anyone point out some simpler code for me to understand...

See here.

"One man's wage rise is another man's price increase." - Harold Wilson

"Fireproof doesn't mean the fire will never come. It means when the fire comes that you will be able to withstand it." - Michael Simmons

"Man who follows car will be exhausted." - Confucius

b-rad3115-Mar-10 8:17

b-rad311

5-Mar-10 8:17

Hi,

Does anyone know what settings I have to change in vc++, for it to allow for the use of the "Decimal" data type as opposed to float or double?

Thanks

Re: the "Decimal" data type in vc++

C^hris L^osinger5-Mar-10 8:19

5-Mar-10 8:19

C++ doesn't have a "Decimal" data type.

there are plenty of decimal classes out there on the net, though. google...[^]

Re: the "Decimal" data type in vc++

Nemanja Trifunovic5-Mar-10 8:25

Nemanja Trifunovic

5-Mar-10 8:25

There is no such setting - decimal floating points are not supported natively by C++ compilers.

Having said that, there are library solutions. Intel® Decimal Floating-Point Math Library[^] deserves taking a look at.

utf8-cpp

Re: the "Decimal" data type in vc++ [modified]

bob1697217-Mar-10 15:39

bob16972

17-Mar-10 15:39

I was interested in checking this out but I keep hitting a brick wall when I try to download it. Did you get this to download from the intel website? What is the trick to getting it to do anything after you accept the license agreement?

*Update*
Never mind, I figured it out.
thanks

modified on Thursday, March 18, 2010 9:09 AM

Re: the "Decimal" data type in vc++

Alain Rist5-Mar-10 9:52

Alain Rist

5-Mar-10 9:52

DECIMAL is a struct defined in Wtypes.h, the (commented out) simple definition is:

/* The following isn't the real definition of Decimal type, */
/* but it is what RPC knows how to remote */
typedef struct tagDEC
    {
    USHORT wReserved;
    BYTE scale;
    BYTE sign;
    ULONG Hi32;
    ULONGLONG Lo64;
    } 	DECIMAL;

So it can represent a signed 96 bits integer with fixed decimal point.

OleAuto.h provides methods to transfer values from C++ numeric types to/from decimal structs such as WINOLEAUTAPI VarR8FromDec( const DECIMAL *pdecIn, DOUBLE *pdblOut); (converts a DECIMAL to DOUBLE) and WINOLEAUTAPI VarDecFromR8(DOUBLE dblIn, DECIMAL *pdecOut); (converts a DOUBLE to DECIMAL);

To use it include Wtypes.h and OleAuto.h, for arithmetic on DECIMAL use the VarDecXXX() functions described at http://msdn.microsoft.com/en-us/library/ms221612.aspx[^].

cheers,
AR

When the wise person points at the moon the fool looks at the finger (Chinese proverb)

Cstring to char

johnalek5-Mar-10 7:03

johnalek

5-Mar-10 7:03

Hi
How to convert CString to char

#sanroop#

Re: Cstring to char

C^hris L^osinger5-Mar-10 7:17

5-Mar-10 7:17

char a = myString.GetAt(0);

Re: Cstring to char

Rajesh R Subramanian5-Mar-10 7:40

Rajesh R Subramanian

5-Mar-10 7:40

CString may have more than one character stored in its internal string array. How do you expect to "convert" it to a char?!

“Follow your bliss.” – Joseph Campbell

vector in space

khomeyni5-Mar-10 7:03

khomeyni

5-Mar-10 7:03

hello
i want to define a vector with three or more parameter in space and as i know vector of stl only gets one parameter ,is there any header in stl or other library to solve this?
also i have an array of points and i want to sort them on one axis ,how i can sort it with sort() of stl without any change to points?
for example i used map for 2 dimension :map<int,int> but when i set for example 11,12 11,13 it is false.
thanks in advance.

Re: vector in space

C^hris L^osinger5-Mar-10 7:21

5-Mar-10 7:21

struct point3D
{
  double x;
  double y;
  double z;
};

std::vector<point3D> my_vector_of_points;

bool sortOnX(const point3D& a, const point3D& b)
{
  return a.x < b.x;
}

std::sort(my_vector_of_points.begin(), my_vector_of_points.end(), sortOnX)