floating-point textbox

[Peteroid]

I want to use a Textbox to allow the user to input a floating point number.
In my case it will always be non-negative. Is there an easy way to do this,
or possibly a link to some sample code that shows how to do this?

Thanks in advance! : )

[==Peteroid==]

[Micus]

"Peteroid" <pe************@msn.com> wrote in message
news:%2******************@TK2MSFTNGP12.phx.gbl...

I want to use a Textbox to allow the user to input a floating point number. In my case it will always be non-negative. Is there an easy way to do this, or possibly a link to some sample code that shows how to do this?

Thanks in advance! : )

[==Peteroid==]

Peteroid,

I did this a year ago and I don't have the code on hand, but essentially
I subclassed the text box and used the STL stringstream class to place the
float from the text box into the stream and then format the output back to
the text box. By doing this, you have control of the precision of the number
(which is correctly rounded) as well as user mistakes (e.g. "10.2k22") being
corrected to a usable float in the output to the text box ("10.2"). I
believe there is atof() conversion involved as well. If time frees up later,
I will send a source example.

HTH, M

[Ioannis Vranos]

Peteroid wrote:

I want to use a Textbox to allow the user to input a floating point number.
In my case it will always be non-negative. Is there an easy way to do this,
or possibly a link to some sample code that shows how to do this?

As far as I know you will have to pass the input string yourself. However
Char::GetNumericValue() may provide much help, it converts a character digit to its
corresponding number value as a double.
For example

Char::GetNumericValue ('4'); returns 4 as a double.
So parsing string "54.145679" can be done like this:

#using <mscorlib.dll>
int main()
{
using namespace System;

String *s= "54.145679";

double d=0;

for(int i= s->Length-1; i>=0; --i)
{
static long nonDecimals= 0;

if(s->Chars[i]=='.')
{
nonDecimals=1;
continue;
}

if(!nonDecimals)
{
d+= Char::GetNumericValue(s->Chars[i]);
d/= 10;
}

else if(nonDecimals)
{
d+= nonDecimals*Char::GetNumericValue(s->Chars[i]);
nonDecimals*=10;
}
}

Console::WriteLine(d);
}

Of course you should validate the contents of the string to be sure it is a valid decimal
number before the conversion, or check the return value of Char::GetNumericValue() (-1.0
in case of error).

[Ioannis Vranos]

Errata fixed:

Ioannis Vranos wrote:

As far as I know you will have to
parse
the input string yourself.
However Char::GetNumericValue() may provide much help, it converts a
character digit to its corresponding number value as a double.
For example

Char::GetNumericValue ('4'); returns 4 as a double.
So parsing string "54.145679" can be done like this:

#using <mscorlib.dll>
int main()
{
using namespace System;

String *s= "54.145679";

double d=0;

for(int i= s->Length-1; i>=0; --i)
{
static long nonDecimals= 0;

if(s->Chars[i]=='.')
{
nonDecimals=1;
continue;
}

if(!nonDecimals)
{
d+= Char::GetNumericValue(s->Chars[i]);
d/= 10;
}

else if(nonDecimals)
{
d+= nonDecimals*Char::GetNumericValue(s->Chars[i]);
nonDecimals*=10;
}
}

Console::WriteLine(d);
}

Of course you should validate the contents of the string to be sure it
is a valid decimal number before the conversion, or check the return
value of Char::GetNumericValue() (-1.0 in case of error).

[Micus]

#include <tchar.h> //for _tstof()
#include <sstream> //for stringstream
#include <iomanip> //for setprecision() and fixed

LRESULT CALLBACK NewTxtBoxWndProc(HWND hwnd, UINT msg, WPARAM wp, LPARAM lp)
{
TCHAR szBuffer[255];
std::basic_stringstream<TCHAR> strm;
double f;

switch(msg)
{
case WM_KILLFOCUS :
GetWindowText(hwnd, szBuffer, 200);
f = _tstof(szBuffer); //convert text to float

//Set format to display numbers as 0.0 (to the nearest tenth)
strm << std::setprecision(1) << std::fixed << f;

//Place formatted number back into text box
SetWindowText(hwnd, strm.str().c_str());

break;
}

return CallWindowProc(OldWndProc, hwnd, msg, wp, lp);
}
then in your main app code, you need to subclass the textbox.

WNDPROC OldWndProc;
oldWndProc = (WNDPROC) SetWindowLong(hwndTextBox, GWL_WNDPROC, (LONG)
NewTxtBoxWndProc);
Regards, M