Delphi Basics : StrToFloat command

DelphiBasics

StrToFloat
Function

Convert a number string into a floating point value

SysUtils unit

1	function StrToFloat(FloatString string):Extended;
2	function StrToFloat (FloatString string; const FormatSettings TFormatSettings:Extended;

Description

The StrToFloat function converts a number string, FloatString such as '123.456' into an Extended floating point number.

It supports integer, floating point, and scientific (exponent) formats.

If a decimal point appears in FloatString, then it must match the current DecimalSeparator value.

Version 2 of this function is for use within threads. You furnish the FormatSettings record before invoking the call. It takes a local copy of global formatting variables that make the routine thread safe.

Notes

The EConvertError exception is thrown if there are errors in FloatString, such as trailing blanks or invalid decimal characters.

Related commands

Extended		The floating point type with the highest capacity and precision
FloatToStr		Convert a floating point value to a string
FloatToStrF		Convert a floating point value to a string with formatting
TFormatSettings		A record for holding locale values for thread-safe functions

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Example code : Converting a scientific format number string

var
  stringValue : string;
  floatValue  : Extended;

begin
  // Set up the source string containing a number representation
  stringValue := '123.456E+002';

  // Convert it to a floating point number
  floatValue  := StrToFloat(stringValue);

  // And display the value
  ShowMessage(stringValue+' = '+FloatToStr(floatValue));
end;

Show full unit code

123.456E+002 = 12345.6

Example code : Catching string conversion errors

var
  A : Extended;

begin
  // We will catch conversion errors
  try
    A := StrToFloat('10 E 2');    // Middle blanks are not supported
  except
    on Exception : EConvertError do
      ShowMessage(Exception.Message);
  end;

  try
    A := StrToFloat('$FF');    // Hexadecimal values are not supported
  except
    on Exception : EConvertError do
      ShowMessage(Exception.Message);
  end;
end;

Show full unit code

'10 E 2' is not a valid floating point value
'$FF' is not a valid floating point value