IsNum

[SMcNeill]

A quick little routine to tell you if a string is a number, or not.

Code: (Select All)

Function IsNum%% (PassedText As String)
    text$ = PassedText
    special$ = UCase$(Left$(text$, 2))
    Select Case special$
        Case "&H", "&B", "&O"
            'check for symbols on right side of value
            r3$ = Right$(text$, 3)
            Select Case r3$
                Case "~&&", "~%%", "~%&" 'unsigned int64, unsigned byte, unsigned offset
                    text$ = Left$(text$, Len(text$) - 3)
                Case Else
                    r2$ = Right$(text$, 2)
                    Select Case r2$
                        Case "~&", "##", "%&", "%%", "~%", "&&" 'unsigned long, float, offset, byte, unsigned integer, int64
                            text$ = Left$(text$, Len(text$) - 2)
                        Case Else
                            r$ = Right$(text$, 1)
                            Select Case r$
                                Case "&", "#", "%", "!" 'long, double, integer, single
                                    text$ = Left$(text$, Len(text$) - 1)
                            End Select
                    End Select
            End Select
            check$ = "0123456789ABCDEF"
            If special$ = "&O" Then check$ = "01234567"
            If special$ = "&B" Then check$ = "01"
            temp$ = Mid$(UCase$(text$), 2)
            For i = 1 To Len(temp$)
                If InStr(check$, Mid$(temp$, i, 1)) = 0 Then Exit For
            Next
            If i <= Len(temp$) Then IsNum = -1
        Case Else
            If _Trim$(Str$(Val(text$))) = text$ Then IsNum = -1
    End Select
End Function

Note that this may fail if you're dealing with values that are so large they translate into scientific notation on you.   "1234567890123456788901234567890" is NOT going to be counted as a number, as QB64 would expect to see this written as "1.234567E30", and your string definitely isn't going to compare to that string.  (And the values probably won't match either, as you lost multiple digits to rounding when it became a scientific notation value.) 

If you look close, you'll see that this function is basically one line of code, unless you happen to be passing it &H, &B, &O values -- in which case it has to work much harder to see if the string you passed it is a valid number, or not.