Thanks for the help, I understood it now; I also found the test progs.
As far I see, it could already be substituted by the following constructs:
program RHelper1v ;
type
poLongint = ^ oLongint ;
oLongint = object
li : longint ;
procedure ShowValue ;
procedure put ( j : longint ) ;
Function inc : poLongint ;
end ;
procedure oLongInt.showvalue ;
begin
Writeln ( 'Value=', li ) ;
end ;
procedure oLongInt.put ( j : longint ) ;
begin
li := j ;
end ;
function oLongInt.inc : polongint ;
begin
system.inc ( li ) ;
result := @self ;
end ;
function v ( i : longint ) : polongint ;
begin
result := addr(i) ;
end ;
var
i : LongInt ;
begin
i := 3 ;
olongint(i).showvalue ;
olongint(i).put ( 4711 ) ;
olongint(i).showvalue ;
olongint(i).inc ;
olongint(i).showvalue ;
olongint(v(12345678)^).put ( 4711 ) ; // senseless, but possible
olongint(v(12345678)^).inc ; // senseless, but possible
olongint(v(12345678)^).showvalue ; // 4712?
end.
And it produces the same assembler code as the construct TYPE HELPER FOR
LONGINT
(which is definitely better readable).
The same program with type helper:
program RHelper1f ;
type
pLongInt = ^ longint ;
tLongIntHelper = type helper for LongInt
procedure ShowValue ;
procedure put ( j : longint ) ;
Function inc : pLongint ;
end ;
procedure TLongIntHelper.showvalue ;
begin
Writeln ( 'Value=', self ) ;
end ;
procedure TLongIntHelper.put ( j : longint ) ;
begin
self := j ;
end ;
function tLongInthelper.inc : plongint ;
begin
system.inc ( self ) ;
result := @self ;
end ;
var
i : LongInt ;
begin
i := 3 ;
i.showvalue ;
i.put ( 4711 ) ;
i.showvalue ;
i.inc ;
i.showvalue ;
12345678.put ( 4711 ) ; // senseless, but possible
12345678.inc ; // senseless, but possible
12345678.showvalue ; // 4712?
end.
The last 3 lines show that the type helpers allow useless code. I assume
such useless code is not catchable by the compiler.
Gerhard
----- Original Message -----
From: "Paul Ishenin" <[email protected]>
To: "FPC developers' list" <[email protected]>
Sent: Friday, February 08, 2013 3:21 PM
Subject: Re: [fpc-devel] Re: [fpc-announce] Feature announcement: Type
helpers
08.02.13, 21:52, Gerhard Scholz wrote:
Maybe I didn't understand the syntax correctly: I didn't see how to get
the value inside the method?
By accessing Self
example:
type
TLongIntHelper = type helper for LongInt
class procedure ShowValue; static;
end;
class procedure TLongIntHelper.Test;
begin
Writeln('Value=',self);
end;
Replace your static class procedure with regular method:
procecure TLongIntHelper.Test;
begin
WriteLn(Self);
end;
Class static method is only needed if you are going to call it for the
type declaration itself like: LongInt.PrintSize:
class procedure TLongIntHelper.PrintSize;
begin
WriteLn(SizeOf(LongInt));
end;
static methods don't have a magic Self variable.
In any case I suggest to look for test which had been commited together
with Sven patch.
Best regards,
Paul Ishenin
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_______________________________________________
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http://lists.freepascal.org/mailman/listinfo/fpc-devel
