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brechtjah

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isdigit ç à è

Nov 19th, 2008

I have absolutely no clue why the following code works except for the following three characters: ç, à and è. It should rule out all non-digit characters from being written into an edit control. Because it let's those three pass trough I am forced to turn this:

 Help with Code Tags 
 cpp Syntax (Toggle Plain Text) 
if(!isdigit(editControl_Content[2]))
if(!isdigit(editControl_Content[2]))

into this:

 Help with Code Tags 
 cpp Syntax (Toggle Plain Text) 
if(editControl_Content[2] == 'è' | editControl_Content[2] == 'ç' | editControl_Content[2] == 'à' | !isdigit(editControl_Content[2]))
if(editControl_Content[2] == 'è' | editControl_Content[2] == 'ç' | editControl_Content[2] == 'à' | !isdigit(editControl_Content[2]))

This is the complete code:

 Help with Code Tags 
 cpp Syntax (Toggle Plain Text) 
char editControl_Content[2];
GetWindowText(GetDlgItem(hwnd, LOWORD(wParam)), &editControl_Content[2], 2);
 
if(editControl_Content[2] == 'è' | editControl_Content[2] == 'ç' | editControl_Content[2] == 'à' | !isdigit(editControl_Content[2])) {
  SetWindowText(GetDlgItem(hwnd, LOWORD(wParam)), NULL);
}
else if(lockOn == false) {
  SetFocus(GetDlgItem(hwnd, LOWORD(wParam)+1));
}
char editControl_Content[2];
GetWindowText(GetDlgItem(hwnd, LOWORD(wParam)), &editControl_Content[2], 2);
            
if(editControl_Content[2] == 'è' | editControl_Content[2] == 'ç' | editControl_Content[2] == 'à' | !isdigit(editControl_Content[2])) {
  SetWindowText(GetDlgItem(hwnd, LOWORD(wParam)), NULL);
}
else if(lockOn == false) {
  SetFocus(GetDlgItem(hwnd, LOWORD(wParam)+1));
}

Any help would be very well appreciated.
Thank you.

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Re: isdigit ç à è

Nov 19th, 2008

First you're using the wrong "OR". For comparisons it's "||", not the bit-operation 'or' "|".

"Jedenfalls bin ich überzeugt, daß der Alte nicht würfelt."
"I became very sensitive to what will happen to all this and all of us." -Two geniuses named Albert

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brechtjah

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Re: isdigit ç à è

Nov 19th, 2008

•

Originally Posted by MosaicFuneral

First you're using the wrong "OR". For comparisons it's "||", not the bit-operation 'or' "|".

My bad, it's 0.20 here, typed it wrong...

EDIT: is this because è, ç, à are Extended ASCII?

Last edited by brechtjah; Nov 19th, 2008 at 7:26 pm.

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Re: isdigit ç à è

Nov 19th, 2008

'ç' has a decimal value of -25, and isdigit() only works with positive signed integer values.

Last edited by Ancient Dragon; Nov 19th, 2008 at 11:24 pm.

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Re: isdigit ç à è

Nov 20th, 2008

See if this works:

 Help with Code Tags 
 C++ Syntax (Toggle Plain Text) 
int isNum(char c)
{
    if((int)c > 47 && (int)c < 58) { return(true); }
    return(false);
}
int isNum(char c)
{
    if((int)c > 47 && (int)c < 58) { return(true); }
    return(false);
}

"Jedenfalls bin ich überzeugt, daß der Alte nicht würfelt."
"I became very sensitive to what will happen to all this and all of us." -Two geniuses named Albert

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Re: isdigit ç à è

Nov 20th, 2008

You are not getting the window text properly, it should be

 Help with Code Tags 
 cpp Syntax (Toggle Plain Text) 
char editControl_Content[2];
// the following gets one char into editControl_Content[0] and sets
// editControl_Content[1] to '\0'
int charCount = GetWindowText(GetDlgItem(hwnd, LOWORD(wParam)), editControl_Content, 2);
if(charCount > 0)
{
    // got a char ...
}
char editControl_Content[2];
// the following gets one char into editControl_Content[0] and sets
// editControl_Content[1] to '\0'
int charCount = GetWindowText(GetDlgItem(hwnd, LOWORD(wParam)), editControl_Content, 2);
if(charCount > 0)
{
    // got a char ...
}

And further on, when you use isdigit(), be sure to use the valid index (0) i.e.

 Help with Code Tags 
 cpp Syntax (Toggle Plain Text) 
if(isdigit(editControl_Content[0]))
...
if(isdigit(editControl_Content[0]))
...

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Re: isdigit ç à è

Nov 20th, 2008

Some notes about isdigit and non-ascii characters:

The isdigit is a C library function (the C library is a part of C++ library) so let's open the C language standard:

•

The header <ctype.h> declares several functions useful for classifying and mapping
characters. In all cases the argument is an int, the value of which shall be representable as an unsigned char or shall equal the value of the macro EOF. If the argument has any other value, the behavior is undefined.

So isdigit domain is 0..255 + EOF macros (usually -1). It's well known that char type may be signed or unsigned. If it's signed, all non-ascii char values implicitly converted to negative integers (formally bad values for all isXXX family).
Fortunately it's so simple to cope with the problem in platform-independent manner, for example:

 Help with Code Tags 
 C++ Syntax (Toggle Plain Text) 
if (isdigit(c&0xFF))    // 1st method
if ((unsigned char)c) // 2nd method
// C++ style radical method #3:
inline bool isDigit(char c) { return c >= '0' && c <= '9'; }
if (isdigit(c&0xFF))    // 1st method
if ((unsigned char)c) // 2nd method
// C++ style radical method #3:
inline bool isDigit(char c) { return c >= '0' && c <= '9'; }

The 3rd method gets the fastest code with a good compiler.

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Re: isdigit ç à è

Nov 20th, 2008

Your second method is broken -- you forgot isdigit. Your third method is not radical.

Negative values will fail when a lookup table is used to implement the function -- they point in memory outside the lookup table.

All my posts may be redistributed under the GNU Free Documentation License.

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Re: isdigit ç à è

Nov 20th, 2008

•

Originally Posted by Rashakil Fol

Your second method is broken -- you forgot isdigit. Your third method is not radical.

Negative values will fail when a lookup table is used to implement the function -- they point in memory outside the lookup table.

#2 Yes, it's annoying misprint

#3 Radical means that it's absolutely implementation-independent method with a very fast instructions generated.
The last remark is a truism.

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brechtjah

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Re: isdigit ç à è

#10

Nov 20th, 2008

•

Originally Posted by mitrmkar

You are not getting the window text properly, it should be
Help with Code Tags

cpp Syntax (Toggle Plain Text)
char editControl_Content[2];
// the following gets one char into editControl_Content[0] and sets
// editControl_Content[1] to '\0'
int charCount = GetWindowText(GetDlgItem(hwnd, LOWORD(wParam)), editControl_Content, 2);
if(charCount > 0)
{
    // got a char ...
}
char editControl_Content[2]; // the following gets one char into editControl_Content[0] and sets // editControl_Content[1] to '\0' int charCount = GetWindowText(GetDlgItem(hwnd, LOWORD(wParam)), editControl_Content, 2); if(charCount > 0) { // got a char ... }
And further on, when you use isdigit(), be sure to use the valid index (0) i.e.
Help with Code Tags

cpp Syntax (Toggle Plain Text)
if(isdigit(editControl_Content[0]))
...
if(isdigit(editControl_Content[0])) ...

That doesn't seem right because when I try this:

 Help with Code Tags 
 cpp Syntax (Toggle Plain Text) 
char editControl_Content[2];
GetDlgItemText(hwnd, LOWORD(wParam), &editControl_Content[2], 2);
 
aString<< editControl_Content[2];
MessageBox(hwnd, aString.str().c_str(), "title", MB_OK);
char editControl_Content[2];
GetDlgItemText(hwnd, LOWORD(wParam), &editControl_Content[2], 2);
            
aString<< editControl_Content[2];
MessageBox(hwnd, aString.str().c_str(), "title", MB_OK);

if I change aString<< editControl_Content[2]; to aString<< editControl_Content[0]; like you're saying I get jibberish, so I put jibberish as argument to isdigit().
Unless I'm mistaken, editControl_Content[2] is a valid argument for isdigit().

Thank