How to check if a string is a number
Checking if a string is a number is quite simple, all we have to do is check if all it's characters are numbers. The situation becomes more complicated when you wish to recognize symbols ('+', '-', '$' etc.), but I'll leave that out for now. This code uses PChar as the parameter for speed reasons. If you want to send a string value to the function just typecast it.
function IsNumber(pcString: PChar): Boolean; begin Result := False; while pcString^ <> #0 do // 0 indicates the end of a PChar string if not (pcString^ in ['0'..'9']) then Exit; Inc(pcString); end; Result := True; end;