Delphi Basics : $ExtendedSyntax command

DelphiBasics

$ExtendedSyntax
Compiler Directive

Controls some Pascal extension handling

{$ExtendedSyntax Off}

1
2	{$ExtendedSyntax On}

Description

The $ExtendedSyntax compiler directive determines whether Delphi includes a number of Pascal language extensions or not.

This affects three areas:

1.Treating functions as procedures

The example code shows the before and after effect of $ExtendedSyntax. When On, Delphi will allow a function result to be ignored - unassigned - thereby treating the function as if it were a procedure.

2.Using Result in functions

With $ExtendedSyntax Off, you must return a function value by assigning to the pseudo variable of the same name as the function. For example : function GetValue : Integer; begin GetValue := 23; end;

With $ExtendedSyntax On, you can also assign to the pseudo variable Result as in the example code.

3.Treating Char arrays as strings

With $ExtendedSyntax On, a zero base array of Char variables can be assigned a string value. It can also be assigned from, as long as the array has a #0 value element to signify the string end.

Notes

$ExtendedSyntax is equivalent to $X.

The default value is $ExtendedSyntax On

$ExtendedSyntax should be set just once in your code.

Related commands

$BoolEval		Whether to short cut and and or operations
$X		Controls some Pascal extension handling
Function		Defines a subroutine that returns a value

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Example code : Fail to compile code that does not assign a function result

begin
  // Set extended syntax off
  {$ExtendedSyntax Off}

  // Call the GetValue function without assigning the result
  GetValue;
end;

// A function that simply returns the value 1
function TForm1.GetValue: Integer;
begin
  Result := 1;
end;

Show full unit code

  Compiltaion fails :

  [Error] Unit1.pas(39): Statement expected, but expression of type 'Integer' found
  [Error] Unit1.pas(45) Undeclared identifier: 'Result'
  [Fatal Error] Project1.dpr(5): Could not compile used unit 'Unit1.pas'

Example code : Code that does not assign a function result compiles OK

begin
  // Set extended syntax on
  {$ExtendedSyntax On}

  // Call the GetValue function without assigning the result
  GetValue;
end;

// A function that simply returns the value 1
function TForm1.GetValue: Integer;
begin
  Result := 1;
end;

Show full unit code

Code compiles OK and runs without doing anything.