C / C++ / MFC

Re: To print two index in a sentence

31-Mar-21 23:49

Try this, which keeps track of the number that are false:

C++

strRslt = "";
int wrong = 0;
for(int i=0; i<4; i++)
{
    if(bCorrect[i] == false)
    {
        if (wrong++ > 0)
            strRslt.AppendFormat("%s", andMsg);
        strRslt.AppendFormat("Q%d", i + 1);
    }
}
if (wrong > 0)
{
    strRslt.AppendFormat("%s", isWrong);
    printf("%s\n", strRslt);
}

CPallini1-Apr-21 0:09

CPallini

1-Apr-21 0:09

Try (not tested, but you get the idea)

C++

bool bAlreadyIncorrect = false;
for(int i=0; i<4; i++)
{ 
  if ( bCorrect[i] == false )
  { 
    if ( bAlreadyIncorrect )
      m_listRslt.AddString(" and ");
    
    strRslt.Format("Q%d", i+1);
    m_listRslt.AddString(strRslt);

    bAlreadyIncorrect = true;
  
  } 
}   

if (bAlreadyIncorrect)
  m_listRslt.AddString( " is wrong");

"In testa che avete, Signor di Ceprano?"
-- Rigoletto

help me

Member 1512893231-Mar-21 4:09

Member 15128932

31-Mar-21 4:09

hello
I need help
Create a class Employee that includes:
1. Three instance variables: a Name(type string), HireYear(type
integer), and a monthly Salary (type double) .
2. A constructor that initializes the three instance variables .
3. Public methods :
a. Set and Get for each instance variable. If the monthly salary
is not positive, do not set its value .
b. GetEmployeeInfo: returns a string contains the employee
name, hire year, and his/her monthly salary.

Re: help me

Richard MacCutchan31-Mar-21 4:17

<algorithm> sort keeps generating error messages.

31-Mar-21 4:17

Member 15128932 wrote:
I need help

Then you need to explain exactly what help you need. If you expect someone to do your work for you, I am afraid you have come to the wrong place. This site is here to help with code that you write.

Re: help me

CPallini31-Mar-21 19:54

CPallini

31-Mar-21 19:54

So..., start coding.
And post here specific questions when you're stuck.

"In testa che avete, Signor di Ceprano?"
-- Rigoletto

c++

Brothers fun28-Mar-21 10:14

Brothers fun

28-Mar-21 10:14

in c++ : (Account Class) Create an Account class that a bank might use to represent customers' bank accounts. Include a data member of type int to represent the account balance. Provide a constructor that receives an initial balance and uses it to initialize the data members. The constructor should validate the initial balance to ensure that it's greater than or equal to 0. If not, set the balance to 0 and display an error message indicating that the initial balance was invalid. Provide three member functions. Member function credit should add an amount to the current balance. Member function debit should withdraw money from the Account and ensure that the debit amount does not exceed the Account's balance. If it does, the balance should be left unchanged and the function should print a message indicating "Debit amount exceeded account balance." Member function getBalance should return the current balance. Create a program that creates at least two Account objects and tests the member functions of class Account.

task 1:derived two classes from Account class

one is bank albilad data members visa, points o

ther is alrajhi bank data members mastercard, points
set and get functions and chargevisa and chargemastercards.

set not exceed account balance.

charge not exceed visa or mastercards balance.

set points visa 10%, mastercards 15%. get functions

Make appropriate member functions const.
task 2:disinherite the classes

classes should share set and get function.

Re: c++

Dave Kreskowiak28-Mar-21 10:40

Dave Kreskowiak

28-Mar-21 10:40

...and you had question about this? What part of this don't you understand, or are having a problem with.

Just posting your homework assignment is not asking a question.

Asking questions is a skill
CodeProject Forum Guidelines
Google: C# How to debug code
Seriously, go read these articles.

Dave Kreskowiak

aschwarz25-Mar-21 22:12

aschwarz

25-Mar-21 22:12

I am trying to get ``sort(begin, end, compare)`` to work, where begin and end are iterators and compare is a boolean function. The Asset constructor is commented out because it generates an error.

I have tried to follow the example in Beginners guide to the std::sort() funct - C++ Articles[^]

This is the code:

C++

class RDA_Names {
   struct Asset {                                        //!< Aseet data
     long long int asset_No   = 0;                       //!< Converted Asset Tracking number
     string        asset_Name = "";                      //!< Normalized Asset Name
     //Asset(long long int asset, string name): asset_No(asset), asset_Name(name) {}
   };

   struct {
      bool compare(const Asset& lhs, const Asset& rhs) { return lhs.asset_No < rhs.asset_No; }
   } comp;

   bool compare(const Asset& x, const Asset& y);
   
   array<Asset, 500> asset_Data;

}; // class RDA_Names

bool RDA_Names::compare(const Asset& lhs, const Asset& rhs) {
   return (lhs.asset_No < rhs.asset_No);
}; // bool RDA_Names::compare(const Asset& x, const Asset& y)

void RDA_Names::post_process_names() {
   sort(asset_Data.begin(), asset_Data.end())           // case 1
   sort(asset_Data.begin(), asset_Data.end(), compare); // case 2
   sort(asset_Data.begin(), asset_Data.end(), comp);    // case 3
}; // void post_process_names()

For each case, the other two cases are commented out. The format of the errors is Error number(repetition), Error text, lines within

C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.28.29910\

where the error was reported.

Case 1:

C2893 (5) Failed to specialize function template 
          \include\algorithm Lines 7361, 7419, 7423, 7434, 7447
C2672 (5) 'operator __surrogate_func': no matching overloaded function found 
          \include\xutility Line 1622

Case 2:

C2780 (1) 'void std::sort(const _RanIt,const _RanIt)': expects 2 arguments - 3 provided	
C2672 (1) 'sort': no matching overloaded function found
C3867 (1) 'RDA_Names::compare': non-standard syntax; use '&' to create a pointer to member

Case 3:

C2064 (5) term does not evaluate to a function taking 2 arguments 
          \include\xutility  Line  1622
          \include\algorithm Lines 7419, 7423, 7434, 7447

Re: <algorithm> sort keeps generating error messages.

Greg Utas26-Mar-21 1:21

Greg Utas

26-Mar-21 1:21

Case 1 fails because there's no comparison function for sort. It might work if Asset defined operator<, but I'd have to check.

EDIT: If you define bool Asset::operator<(const Asset& that), then case 1 also compiles.

Case 2 fails because compare takes a this pointer. If a comparison function is going to be part of a class, it needs to be declared static.

Case 3, I'd have to investigate. I've used this struct technique, but only for a set I believe. It's likely that array doesn't use it.

Try making your compare function a free function (outside the class) or static and see what happens in case 2. In the meantime, I'll look at this further.

* * *

Fixing case 2 looks like the way to go. I compiled the following successfully, and the constructor didn't give me any problems:

C++

class RDA_Names {
   struct Asset { 
     long long int asset_No   = 0; 
     string        asset_Name = ""; 
     Asset(long long int asset, string name): asset_No(asset), asset_Name(name) {}
   };

// struct {
//    bool compare(const Asset& lhs, const Asset& rhs) { return lhs.asset_No < rhs.asset_No; }
// } comp;

   static bool compare(const Asset& x, const Asset& y);

   void post_process_names();
   
   array<Asset, 500> asset_Data;

}; // class RDA_Names

bool RDA_Names::compare(const Asset& lhs, const Asset& rhs) {
   return (lhs.asset_No < rhs.asset_No);
}; // bool RDA_Names::compare(const Asset& x, const Asset& y)

void RDA_Names::post_process_names() {
// sort(asset_Data.begin(), asset_Data.end());           // case 1
   std::sort(asset_Data.begin(), asset_Data.end(), compare); // case 2
// sort(asset_Data.begin(), asset_Data.end(), comp);    // case 3
}; // void post_process_names()

Robust Services Core | Software Techniques for Lemmings | Articles
The fox knows many things, but the hedgehog knows one big thing.

modified 26-Mar-21 8:55am.

Re: <algorithm> sort keeps generating error messages.

aschwarz26-Mar-21 6:48

aschwarz

26-Mar-21 6:48

Although it's a waste of time to say this,
And I know you've heard it before.
But your answers were most pointed
And it clearly went to the fore.

We thank you all
My wife because I don't grumble
I with nothing to grumble about.

I have tried to follow all of your suggestions (my following is full). I now have pointers or references everywhere and the thing seems to compile without complaint. Now to get rid of those damn'd nuisance run-time errors.

thanks!

Re: <algorithm> sort keeps generating error messages.

Mircea Neacsu26-Mar-21 2:40

Re: <algorithm> sort keeps generating error messages.

26-Mar-21 2:40

To complement what Greg was saying:
- case 3 fails because comp is a structure not a function returning a bool. Try changing it to:

C++

bool comp (const RDA_Names::Asset& lhs, const RDA_Names::Asset& rhs)
{
  return lhs.asset_No < rhs.asset_No;
}

You will have to also make Asset structure public.

As a case 4 you can try this:

C++

sort (asset_Data.begin (), asset_Data.end (), [](auto& l, auto& r)->bool {
  return l.asset_No < r.asset_No; });

where the comparison function is an anonymous lambda.

The next step is to look at how efficient your code will be. If you are sorting only 500 objects and you don't do it too often, it's probably OK. In general however your solution is highly inefficient. Every time sort has to exchange two elements it makes copies of the asset_Name string.

There are various ways to improve it:
- keep a unique_ptr pointer to string and provide a move constructor for the Asset structure.
- create an array of indexes in RDA_Names and sort it inseted of sorting the asset_Data array.

Mircea

modified 26-Mar-21 9:14am.

aschwarz26-Mar-21 10:27

aschwarz

26-Mar-21 10:27

Your first point is right on, and gets me back to Case 2. You're second point is incorrect. What is being sorted is an object of some type. The sort routine ignores the type and whether the object containing the type is private or public. It only works on comparison, I assume signed char comparison if there is no comparison function, and the ability to index and swap. The comparison function has no cognizance of privacy, it is only passed pointers/objects and returns a bool.

At the sort base level, the input object need not be public, and if the input object contains objects, these contained objects need not be public.

Just guessing.
thanks

Re: <algorithm> sort keeps generating error messages.

Mircea Neacsu26-Mar-21 12:22

26-Mar-21 12:22

Quote:
Just guessing.

Well, you didn't guess right Smile | :)

Pretty much all you said is valid for the old C qsort function. std::sort is an entirely different beast. I suggest you carefully read the description at std::sort - cppreference.com[^]

Quote:
The sort routine ignores the type and whether the object containing the type is private or public.

I'm not sure I understand what you mean by "the object containing the type". In C++ objects don't contain types. Besides the sort routine is not ignoring the object type at all. According to C++ reference: "The type of dereferenced RandomIt must meet the requirements of MoveAssignable and MoveConstructible". That requires at least a copy constructor for the object (either user defined or generated by the compiler).

Quote:
The comparison function has no cognizance of privacy, it is only passed pointers/objects and returns a bool.

Of course not, the comparison function needs to access the members of the object in order to compare them. Either it is a member function or a friend function or the members in question are public.

The example on the C++ reference page mentioned above shows all the different methods you can use to invoke the std::sort algorithm.

Mircea

Win32 Structures

Richard Andrew x6414-Mar-21 9:52

Richard Andrew x64

14-Mar-21 9:52

My knowledge of the low level implementation of C++ structures and classes is limited.

But I want to ask someone who might know, is it theoretically possible to derive a class from a Win32 structure and add methods and still be able to pass the new "structure" to a Win32 API?

I do know that adding class data members would be out of the question, because that would change the size of the structure.

But is adding methods to a structure something I could do and still use it in the windows api?

The difficult we do right away...
...the impossible takes slightly longer.

Mircea Neacsu14-Mar-21 10:22

14-Mar-21 10:22

Yes, it is very much possible. You can write something like this:

C++

class MyPen : public LOGPEN {
  public:
    MyPen (/*args*/);
    void use_pen ();
  private:
    int stuff;
}

MyPen the_pen;
HPEN hp = CreatePenIndirect ((LOGPEN*)&the_pen);

Note that you can also extend your object with additional data members. They will be placed after the base class (Windows structure) and they will do no harm.

Mircea

Richard Andrew x6414-Mar-21 10:32

Richard Andrew x64

14-Mar-21 10:32

Thanks for your reply. I'm excited to try this.

Your example is great. But if I wanted to use an array of MyPen's then that would surely cause problems because of the larger size, no?

The difficult we do right away...
...the impossible takes slightly longer.

Mircea Neacsu14-Mar-21 10:36

14-Mar-21 10:36

Correct but only if the Windows API call takes an array of (the smaller) structures as parameters. Of top of my head, I cannot think of one that does.

Mircea

11917640 Member 17-Mar-21 3:01

11917640 Member

17-Mar-21 3:01

This is the way some MFC classes are implemented:

C++

typedef struct tagPOINT
{
    LONG  x;
    LONG  y;
} POINT, *PPOINT, NEAR *NPPOINT, FAR *LPPOINT;

class CPoint :
	public tagPOINT
{
    ...
};

No additional members and virtual functions to get binary compatibility with underlying structure.

Richard Andrew x6417-Mar-21 9:20

Richard Andrew x64

17-Mar-21 9:20

Hi, thanks very much for your post.

Do I understand correctly that non-virtual functions would ruin binary compatibility?

The difficult we do right away...
...the impossible takes slightly longer.

Zoom image on mouse position

11917640 Member 17-Mar-21 19:19

11917640 Member

17-Mar-21 19:19

Non-virtual functions don't change a class instance size. You can use this technique, as in existing Microsoft classes like CPoint, CRect, adding instance non-virtual functions and static functions, if necessary.

Gopi Nath12-Mar-21 0:20

Gopi Nath

12-Mar-21 0:20

Hello,

I am displaying an image in a static control (in a dialog) and trying to stretch according to the zoom factor on mouse position. Zoom on mouse position is working fine, but the image is not fitting inside the static control, going all over the dialog.

Below is the code.

C++

// source image
	Gdiplus::Bitmap *gpBitmap = new Gdiplus::Bitmap(mImagePath);

	int origW = gpBitmap->GetWidth(); // 5298 - original width
	int origH = gpBitmap->GetHeight(); // 2728 - original height

	// destination rectangle
	RECT rcVPC;
	GetClientRect(hWnd, &rcVPC); // 501 X 255 - size of the static control
	HDC hDc = GetDC(hWnd);

	float perW = (float)rcVPC.right / (float)origW;
	float perH = (float)rcVPC.bottom / (float)origH;
		
	int newW = origW * perW * mVPZoomFactor; // starting factor is 1.0 and multiplying with 1.2 with each zoom
	int newH = origH * perH * mVPZoomFactor;

	Gdiplus::Bitmap *bmpResized = new Gdiplus::Bitmap(newW, newH, gpBitmap->GetPixelFormat());
	Gdiplus::Graphics *graphics = new Gdiplus::Graphics(bmpResized);
	graphics->DrawImage(gpBitmap, 0, 0, newW, newH);
	
	int zoomWidth = (int)(0.5 + newW * mVPZoomFactor);
	int zoomHeight = (int)(0.5 + newH * mVPZoomFactor);

	//Find the position "factor"
	double dXFactor = (double)rcVPC.right / stX; // stX, stY - mouse position on zoom
	double dYFactor = (double)rcVPC.bottom / stY;

	//Find the origin
	int left = stX - zoomWidth / dXFactor;
	int right = stY - zoomHeight / dYFactor;

	HBRUSH   hB = GetSysColorBrush(COLOR_3DDKSHADOW);

	FillRect(hDc, &rcVPC, hB);

	HDC hdcMem = CreateCompatibleDC(hDc);

	bmpResized->GetHBITMAP(0, &hBmpVPCanvas);

	HBITMAP oldBmp = (HBITMAP)SelectObject(hdcMem, hBmpVPCanvas);

	//use StretchBlt
	StretchBlt(hDc, left, right, zoomWidth, zoomHeight, hdcMem, 0, 0, newW, newH, SRCCOPY);

	SelectObject(hdcMem, oldBmp);

	DeleteDC(hdcMem);

	delete gpBitmap;

Can anyone help me, what i am doing wrong?

Regards,
Gopinath.

Re: Zoom image on mouse position

Richard MacCutchan12-Mar-21 1:28

Re: Zoom image on mouse position

12-Mar-21 1:28

Gopi Nath wrote:
what i am doing wrong?

Probably mixing GDI and GDI+; you should only use one of these, preferably GDI+. Zooming an image is quite simple in GDI+ as you just need to specify the target rectangle's position and size.

Gopi Nath14-Mar-21 20:34

Gopi Nath

14-Mar-21 20:34

Thank you Richard, tried with GDI+ only with some changes, now, i am able to get the required output.

Regards,
Gopinath.

Select TRACE functions based on both a variable and a #define?

arnold_w11-Mar-21 5:31

arnold_w

11-Mar-21 5:31

I'm working on an embedded ARM-project (STM32F) and I'm programming in C programming language and compiling with Eclipse/GCC. In the project there is TRACE functionality implemented that, if enabled, logs various things over UART using queues and DMA:

C++

#define TRACE(grp, lvl, ...) traceToPrintStream(grp, __FILE__, __FUNCTION__, __LINE__, lvl, __VA_ARGS__)

It can be used, e.g. like this:

C++

TRACE("regCallbacks", T_D, "The user pressed the button");
TRACE("regCallbacks", T_D, "Write to reg %d. First written byte: 0x%X", regAddr, regValues[0]);

I need a different trace that is not queued, does not use DMA and does not include the file name, function name and line number, but the other persons in this project do not agree to throw out the existing TRACE, so I need to make something in parallel. I want to be able to enable my TRACE in two ways, either by #defines:

C++

#define ENABLE_USER_EVENTS_LOGGING
#define ENABLE_COMMUNICATOIN_BUS_LOGGING

or by setting a varible during runtime:

C++

Bool_t enableCommunicationBusLogging;
Bool_t enableUserEventsLogging;

I need a different grouping (the grp parameter) than the others, so the example TRACEings above would have to be augmented with my grouping as well:

C++

TRACE_EX("regCallbacks", USER_EVENTS, T_D, "The user pressed the button");
TRACE_EX("regCallbacks", COMMUNICATION_BUS, T_D, "Write to reg %d. First written byte: 0x%X", regAddr, regValues[0]);

The rules I would like to apply are:
1. If my TRACE is enabled using the macros (hardcode enabled), then the other TRACE can not be used (hardcode disabled).
2. If my TRACE is not enabled using the macros, then both TRACEs can be enabled/disabled during runtime independently of each other. However, they are enabled per groups!

Does anybody know how I can solve this? I found a great website (C Preprocessor tricks, tips, and idioms · pfultz2/Cloak Wiki · GitHub[^]) that shows some really neat macro-tricks, but I'm not sure how to apply it my case.

Re: Select TRACE functions based on both a variable and a #define?

Richard MacCutchan11-Mar-21 6:11