SysUtils.StrToFloat Function

Converts a given string to a floating-point value.

Pascal

function StrToFloat(const S: string): Extended; overload;
function StrToFloat(const S: string; const FormatSettings: TFormatSettings): Extended; overload;

C++

Extended StrToFloat(const AnsiString S);
Extended StrToFloat(const AnsiString S, const TFormatSettings FormatSettings);

File

SysUtils

Description

Use StrToFloat to convert a string, S, to a floating-point value. S must consist of an optional sign (+ or -), a string of digits with an optional decimal point, and an optional mantissa. The mantissa consists of 'E' or 'e' followed by an optional sign (+ or -) and a whole number. Leading and trailing blanks are ignored.

The DecimalSeparator global variable or its TFormatSettings equivalent defines the character that is used as a decimal point. Thousand separators and currency symbols are not allowed in the string. If S doesn't contain a valid value, StrToFloat raises an EConvertError exception.

The first form of StrToFloat is not thread-safe, because it uses localization information contained in global variables. The second form of StrToFloat, which is thread-safe, refers to localization information contained in the FormatSettings parameter. Before calling the thread-safe form of StrToFloat, you must populate FormatSettings with localization information. To populate FormatSettings with a set of default locale values, call GetLocaleFormatSettings.

C++ Examples:

Copy Code

/*
The following example uses two buttons, a string grid, and
text edit on a form. When the conversion button is clicked,
the values across the top of the string grid are converted
using the formats along the left side.  Select a cell and
use the Alter Cell button and text edit to change the
values converted and the conversion formats.
*/
void __fastcall TForm1::Button1Click(TObject *Sender)
{
  for (int x = 1; x < StringGrid1->ColCount; x++)
  {
    for (int y = 1; y < StringGrid1->RowCount; y++)
    {
      StringGrid1->Cells[x][y] = FormatFloat(
      StringGrid1->Cells[0][y], StrToFloat(StringGrid1->Cells[x][0]));
    }
  }
}

int currCellCol, currCellRow;

void __fastcall TForm1::StringGrid1MouseUp(TObject *Sender, TMouseButton Button,
      TShiftState Shift, int X, int Y)
{
  StringGrid1->MouseToCell(X, Y, currCellCol, currCellRow);
}

// Alter Cell
void __fastcall TForm1::Button2Click(TObject *Sender)
{
  StringGrid1->Cells[currCellCol][currCellRow] = Edit1->Text;
}

void __fastcall TForm1::FormCreate(TObject *Sender)
{
  StringGrid1->Cells[1][0] = "1234";
  StringGrid1->Cells[2][0] = "-1234";
  StringGrid1->Cells[3][0] = "0.5";
  StringGrid1->Cells[4][0] = "0";
  StringGrid1->Cells[0][1] = "";
  StringGrid1->Cells[0][2] = "0";
  StringGrid1->Cells[0][3] = "0.00";
  StringGrid1->Cells[0][4] = "#.##";
  StringGrid1->Cells[0][5] = "#,##0.00";
  StringGrid1->Cells[0][6] = "#,##0.00;(#,##0.00)";
  StringGrid1->Cells[0][7] = "#,##0.00;;Zero";
  StringGrid1->Cells[0][8] = "0.000E+00";
  StringGrid1->Cells[0][9] = "#.###E-0";
}

Delphi Examples:

Copy Code

{
The following example uses two buttons, a string grid, and
text edit on a form. When the conversion button is clicked,
the values across the top of the string grid are converted
using the formats along the left side.  Select a cell and
use the Alter Cell button and text edit to change the
values converted and the conversion formats.
}
procedure TForm1.Button1Click(Sender: TObject);
var
  X, Y, I: Integer;
begin
  for X := 1 to StringGrid1.ColCount - 1 do
  begin
    for Y := 0 to StringGrid1.RowCount - 1 do
    begin
      StringGrid1.Cells[X,Y] := SysUtils.FormatFloat(
        StringGrid1.Cells[0,Y], StrToFloat(StringGrid1.Cells[X,0]));
    end;
  end;

end;

var currCellCol, currCellRow: Integer;

// Alter Cell
procedure TForm1.Button2Click(Sender: TObject);
begin
  StringGrid1.Cells[currCellCol,currCellRow] := Edit1.Text;
end;

procedure TForm1.StringGrid1MouseUp(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
begin
  StringGrid1.MouseToCell(X, Y, &currCellCol, &currCellRow);
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
  StringGrid1.Cells[1,0] := '1234';
  StringGrid1.Cells[2,0] := '-1234';
  StringGrid1.Cells[3,0] := '0.5';
  StringGrid1.Cells[4,0] := '0';
  StringGrid1.Cells[0,1] := '';
  StringGrid1.Cells[0,2] := '0';
  StringGrid1.Cells[0,3] := '0.00';
  StringGrid1.Cells[0,4] := '#.##';
  StringGrid1.Cells[0,5] := '#,##0.00';
  StringGrid1.Cells[0,6] := '#,##0.00;(#,##0.00)';
  StringGrid1.Cells[0,7] := '#,##0.00;;Zero';
  StringGrid1.Cells[0,8] := '0.000E+00';
  StringGrid1.Cells[0,9] := '#.###E-0';
end;

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