I know that the examples are stupid and most of them senseless. Sometimes I used similar workarounds (more senseful), so I just wanted to know if the type helper construct produces more efficient code. It doesn't.
> The main advantage of helpers compared to your example is that the compiler will do the type checking. That's an advantage. >> 12345678.showvalue ; // 4712? >And the last line should show 12345678 hopefully :) Yes. it does. Greetings Gerhard ----- Original Message ----- From: Sven Barth To: FPC developers' list Sent: Friday, February 08, 2013 8:24 PM Subject: Re: [fpc-devel] Re: [fpc-announce] Feature announcement: Type helpers Am 08.02.2013 19:52 schrieb "Gerhard Scholz" <g...@g--s.de>: > > 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). Impressive O.o I would have never thought to use objects like that. The main advantage of helpers compared to your example is that the compiler will do the type checking. > 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. If we could keep track of writes to Self and then mark the methods accordingly we could at least provide a warning or a hint. And the last line should show 12345678 hopefully :) Regards, Sven _______________________________________________ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-devel _______________________________________________ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-devel
