Re: test if a string is a valid 'number'?

"Tom Serface" <>
Wed, 30 May 2007 11:55:31 -0700
Point taken. I didn't know his strings would be that complex. I guess the
only way to do it completely would be to loop through the string. I suppose
you could do something like (I just wrote this out, didn't really test it,
but you get the idea):

bool IsANumber(const CString& cs)
   LPCTSTR szTest = cs;
   bool bFoundDot = *szText == _T('.');
   bool bNum = true;

   //If we have a + or - it should be in the first position. Also could be
decimal point or a number
   if ((*szTest > _T('9') || *szTest < _T('0')) && *szTest != _T('-') &&
*szText != _T('+') && !bFoundDot)
         bNum = false;

   while (bNum && *szTest) {
      // We only want one decimal point
      if(!bFoundDot && *szTest != _T('.'))
           bFoundDot = true;
      else if (*szTest > _T('9') || *szTest < _T('0')) {
         bNumeric = false;

   return bNum;

Of course you could add a lot ot this for other kinds of tests (like
scientific notation. If you already have reg ex in your code then your way
is likely better.


"MrAsm" <> wrote in message

On Wed, 30 May 2007 10:23:12 -0700, "Tom Serface"
<> wrote:

If you are using a CString you can use the SpanExcluding() function to
if all of the characters are numbers, +, -, or period. Something like:

CString result = csNumber.SpanExcluding(_T("0123456789+-."));

Then if result it not empty (result.IsEmpty()) then you know there are
other characters in the list.


Hi Tom,

but if result is empty, it could be *not* a number, e.g.

 csNumber = _T("++332.-232.+2002+-22-1+");

is it correct?


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