Comments on: More undocumented Win32 language features

By: Roozbeh GHolizadeh

Roozbeh GHolizadeh — Wed, 05 Oct 2005 11:06:02 +0000

Well i think this is also undocumented!
in delphi help about virtual methods in properties stated
"If fieldOrMethod is a method, it cannot be dynamic and, if virtual, cannot be overloaded"

but following code compiles fine

myclass=class
procedure SetTestValue(invalue : integer);overload;virtual;
procedure SetTestValue(invalue : string);overload;virtual;
property testvalue:integer write SetTestValue;
end;

and doesnt compile in delphi 7!

i also found this intresting thing(i dont know if in help stated or not)

property only works with first overloaded procedure so the following doesnt compile!

procedure SetTestValue(invalue : integer);overload;virtual;
procedure SetTestValue(invalue : string);overload;virtual;
property testvalue:string write SetTestValue;

forgive me if all was documented and told before ;)

By: Laurent Dardenne

Laurent Dardenne — Wed, 08 Jun 2005 08:27:05 +0000

And too, Strict private, Private, Public directive inside a record:

unit TestRecord;

interface
Type
TUrec = record
Strict private
StrictPrivateValue : integer;
Private
PrivateValue : integer;
Public
PublicValue: Integer;
end;

implementation
end.

program TestRec;

{$APPTYPE CONSOLE}

uses
SysUtils,
TestRecord in 'TestRecord.pas';

type
Trec = record
Strict private
StrictPrivateValue : integer;
Private
PrivateValue : integer;
Public
PublicValue: Integer;
end;

var TR : Trec;
TUR :TUrec;

begin

with TR do
begin
StrictPrivateValeur:=1;
PrivateValeur:=2;
PublicValeur:=3;
end;

with TUR do
begin
//StrictPrivateValeur:=1; // error E2003 : Identifier not declared 'StrictPrivateValeur'
//PrivateValeur:=2; // error E2003 : Identifier not declared'PrivateValeur'
PublicValeur:=3;
end;

end.

By: Laurent Dardenne

Laurent Dardenne — Wed, 08 Jun 2005 07:55:45 +0000

There is also the Initialize method. To initialize an array :

A := TDoubleArray.Create(1.7, 3.9, 17.1, 39.7, 42.0);

Writeln(’Size =’,Length(A));

for D in A do

Writeln(D:1:1);

Initialize(A);

Writeln(’Size =’,Length(A));

By: Jim McKeeth

Jim McKeeth — Thu, 26 May 2005 22:08:35 +0000

That is some major fun! Thanks for sharing these finds!

By: Rudy Velthuis

Rudy Velthuis — Fri, 13 May 2005 14:48:52 +0000

<<
Actually, experimental units are documented in 2005.
>>

Oh cool, I was not aware of that.

<<
With these directives, do they actually work (i.e. are they enforced in the compiler/language), or does the compiler ignore them and not error? For some of these it's obvious that they must work (e.g. overloaded default array properties), but for the directives it may not be so clear.
>>

Abstract, when used for classes, does not have any useful meaning I could find in the online help, so I did not test that. But the "sealed" directive is enforced, i.e. you can't extend a sealed class.

AFAIK, "final" is also enforced.

By: Anthony Frazier

Anthony Frazier — Fri, 13 May 2005 12:26:19 +0000

Actually, experimental units are documented in 2005. The following is the help link where its documented.

ms-help://borland.bds3/bds3guide/html/DeclarationsAndStatements.htm

With these directives, do they actually work (i.e. are they enforced in the compiler/language), or does the compiler ignore them and not error? For some of these it's obvious that they must work (e.g. overloaded default array properties), but for the directives it may not be so clear.