DelphiBasics
Val
Procedure
Converts number strings to integer and floating point values System unit
 procedure Val ( const NumberString : string; var NumberVar : Number Type; var ErrorCode : Integer ) ;
Description
The Val procedure is an older Delphi procedure that can convert a string NumberString into both integer and floating point variables.
 
The variable NumberVar must be appropriate to the number string. Specifically, an integer string value must be provided when NumberVar is an Integer type.
 
If the conversion succeeds, then ErrorCode is set to 0. Otherwise, it is set to the first character in NumberString that failed the conversion.
Notes
Warning : it is safer to use the SysUtils conversion routines, such as StrToFloat where locale information is recognised. In particular, the character used for the decimal point.
Related commands
Chr Convert an integer into a character
IntToStr Convert an integer into a string
StrToInt Convert an integer string into an Integer value
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Example code : Illustrate successful and unsuccessful floating point number string conversions
// Full Unit code.
// -----------------------------------------------------------
// You must store this code in a unit called Unit1 with a form
// called Form1 that has an OnCreate event called FormCreate.
 
unit Unit1;
 
interface
 
uses
  // The System unit does not need to be defined
  Forms, Dialogs;
 
type
  TForm1 = class(TForm)
    procedure FormCreate(Sender: TObject);
  end;
 
var
  
Form1: TForm1;
 
implementation
{$R *.dfm} // Include form definitions
 
procedure TForm1.FormCreate(Sender: TObject);

var
  numberString : string;
  float        : Extended;
  errorPos     : Integer;
begin
  // Set up a valid floating point number string
  numberString := '12345.678';

  // Convert it into a value
  Val(numberString, float, errorPos);

  // Display the string and converted value
  if errorPos = 0
  then ShowMessageFmt('Val(%s) = %12.3f',[numberString,float]);

  // Val ignores the Decimal Separator - SysUtils converters don't
  DecimalSeparator := '_';
  numberString := '12345_678';
  Val(numberString, float, errorPos);
  if errorPos = 0
  then ShowMessageFmt('Val(%s) = %12.3f',[numberString,float])
  else ShowMessageFmt('Val(%s) failed at position %d',
                      [numberString, errorPos]);
end;
 
end.
Hide full unit code
   Val(12345.678) = 12345.678
   Val(12345_678) failed at position 6
 
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