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

From:

"Tom Serface" <tom.nospam@camaswood.com>

Newsgroups:

microsoft.public.vc.mfc

Date:

Wed, 30 May 2007 11:55:31 -0700

Message-ID:

<2D00186E-20C5-4D9A-BCF0-A49510B71D40@microsoft.com>

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;

   ++szTest;
   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;
         break;
      }
      ++szTest;
   }

   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.

Tom

"MrAsm" <mrasm@usa.com> wrote in message
news:v5er539sq6meroel6813g04161rms44o7f@4ax.com...

On Wed, 30 May 2007 10:23:12 -0700, "Tom Serface"
<tom.nospam@camaswood.com> wrote:

If you are using a CString you can use the SpanExcluding() function to
check
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.

Tom

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?

MrAsm