Pointer problem (surprise, surprise) in Visual C++

[cannymonkey]

Hi,

I am very new to C++ (i.e. only begun using it in the last few weeks) and am currently maintaining an existing .dll file for the company i work for. After reading quite a few threads in this forum i see that the main sticking point for many newbies appears to be pointers, and i am no exception. I want to really grasp the concept of pointers and could use a really good explanation (if you know of any particularly good websites, please feel free to post a link).

Now, my current question concerns a call to a function, passing a character array.....

...
...
...
char buffer1[10], buffer2[10];
 
GetDlgItemText(hWnd, IDC_C_LOW, buffer1, 10);
GetDlgItemText(hWnd, IDC_C_UP, buffer2, 10);
 
if( !checkFloatInput(buffer1) || !checkFloatInput(buffer2) )
{
  EndDialog(hWnd, TRUE); // destroy the convexity dialog box
  convexMin = 0;
  convexMax = 0; // reset values
 
  // simulated left-click
  Convex_LtClick(NULL, NULL, NULL, NULL, NULL, hWnd, NULL); 
  break;
}
...
...
...
 

And the code for the checkFloatInput function is below:

BOOL checkFloatInput(char aCharArray[]) //used to error-trap non-float data entered by the user
{
 
    int tempAsciiValue;
    bool result = true;
    int numOfDecimalPts = 0; //
    char errorMsg[60] = "Invalid input:\n\n";
 
    for( int i = 0; i < int(strlen(aCharArray)); i++ )
    {
      tempAsciiValue = int(aCharArray[i]); // ascii value for character being considered
 
      if( tempAsciiValue==46 || ( tempAsciiValue > 47 && tempAsciiValue < 58) )
      {
        if( tempAsciiValue==46 && numOfDecimalPts > 0 )
        {
            i = strlen(aCharArray); // force end of for-loop
            strcat(errorMsg, " - Cannot have more than one decimal point.\n\nPlease re-enter.");
            MessageBox(NULL,(LPCSTR)errorMsg, NULL, MB_OK);
            result = false;
        }
        else if( tempAsciiValue==46 && numOfDecimalPts == 0 )
        {
            numOfDecimalPts++; // 
            aCharArray++; // move to next character in the array
        }
        else
            aCharArray++; // move to next character in the array
      }
      else
      {
          i = strlen(aCharArray); // force end of for-loop                    
          strcat(errorMsg, " - Non-numeric characters entered.\n\nPlease re-enter.");
          MessageBox(NULL,(LPCSTR)errorMsg, NULL, MB_OK);
          result = false;
      }
 
    }// end of for-loop
 
    return result;
 
} // end of checkFloatInput function
 

The error message i get when compiling is as below:-

error C3861: 'checkFloatInput': identifier not found
error C3861: 'checkFloatInput': identifier not found
error C2365: 'checkFloatInput' : redefinition; previous definition was 'formerly unknown identifier'

The problem appears to be the parameter i am passing in the if-statement. I have tried many permutations of how the parameter is passed and how it is received in the function, but frustratingly, i am always getting compile errors. I am sure the answer is very simple and it is just my lack of experience with pointers that is the problem - I am hastily reading up on the subject, but i am also trying to learn Matlab and OriginPro at the same time, and any help would be much appreciated.

Thanks,

Phil

[oler1s]

http://msdn2.microsoft.com/en-us/lib...yx(vs.71).aspx

Tip: Google can come in especially handy. So will MSDN when using Visual C++ and using WinAPI calls.

Diagnosis: Problem isn't the code within your function. The function itself is being called incorrectly. You have to pass in precisely the right number of parameters, and the correct type for each argument to the function when it is called.

[cannymonkey]

Tip: Google can come in especially handy. So will MSDN when using Visual C++ and using WinAPI calls.

Diagnosis: Problem isn't the code within your function. The function itself is being called incorrectly. You have to pass in precisely the right number of parameters, and the correct type for each argument to the function when it is called.

Hi, thanks for getting back to me. I had already checked MSDN and had seen the page you recommended, but it still isn't quite 'clicking' in my mind yet. From MSDN, i understand that the GetDlgItemText(HWND hDlg, int nIDDlgItem, LPTSTR lpString, int nMaxCount) function takes the user's input and puts the string into a buffer pointed to by lpString.

I did some more reading (a pretty good intro to pointers in C can be found here for any other newbie's out there) around this area and amended my calling code as below:-

char* buffer1 = "";
char* buffer2 = "";
 
UINT sizeBuffer1 = GetDlgItemText(hWnd, IDC_C_LOW, buffer1, 10);
UINT sizeBuffer2 = GetDlgItemText(hWnd, IDC_C_UP, buffer2, 10);
 
// Note, that buffer1 and buffer2 are pointers to buffers where text is stored.
 
if( !checkFloatInput(buffer1, sizeBuffer1) || !checkFloatInput(buffer2, sizeBuffer2) )
{
   EndDialog(hWnd, TRUE); // destroy the convexity dialog box
  ....
....
....
 

I also amended my function a little, as below:-

BOOL checkFloatInput(char * aCharArray, UINT sizeOfArray) //used to error-trap non-float data entered by the user
{
 
  int tempAsciiValue;
  bool result = true;
  int numOfDecimalPts = 0; //
  char errorMsg[60] = "Invalid input:\n\n";
 
  for( int i = 0; i < (int)sizeOfArray; i++ )
  {
    tempAsciiValue = int(aCharArray); // ascii value for character being considered
 
    if( tempAsciiValue==46 || ( tempAsciiValue > 47 && tempAsciiValue < 58) )
    {
        if( tempAsciiValue==46 && numOfDecimalPts > 0 )
        {
    i = (int)sizeOfArray; // force end of for-loop
    strcat(errorMsg, " - Cannot have more than one decimal point.\n\nPlease re-enter.");
    MessageBox(NULL,(LPCSTR)errorMsg, NULL, MB_OK);
    result = false;
        }
        else if( tempAsciiValue==46 && numOfDecimalPts == 0 )
        {
    numOfDecimalPts++; // 
    aCharArray++; // move to next character in the array
        }
        else
              aCharArray++; // move to next character in the array
    }
   else
   {
       i = (int)sizeOfArray; // force end of for-loop                
       strcat(errorMsg, " - Non-numeric characters entered.\n\nPlease re-enter.");
       MessageBox(NULL,(LPCSTR)errorMsg, NULL, MB_OK);
       result = false;
    }
 
  }// end of for-loop
 
  return result;
 
} // end of checkFloatInput function
 
 

However, i am still getting the same compilation error message. My thinking at present is that, when i call checkFloatInput(buffer1, sizeBuffer1), buffer1 is a pointer to a char array and as the checkFloatInput() function is set up to take a char pointer as one of it's arguments, this should work - I have tried passing buffer1 as &(*buffer1[0]) also, as well as quite a few other variations but always get the same error, "error C3861: 'checkFloatInput': identifier not found". I have googled the issue of 'error C3861', 'passing char arrays' and variations on that theme but as i say, unfortunately something hasn't gone eureka in my mind yet and still need some advice if there is anything else you could recommend. I am sure that the problem is with an assumption i am making about pointer types that i haven't yet corrected.

Cheers for any further light you may be able to shed.

Phil