If you declare a parameter as const does that effectively behave like passing by reference? I have some performance sensitive functions that take records as arguments and I don’t want copying to the stack so I’ve been using @ but maybe const is just as good? Thanks.

Regards,
Ryan Joseph

Ryan Joseph wrote

If you declare a parameter as const does that effectively behave like passing by reference? I have some performance sensitive functions that take records as arguments and I don’t want copying to the stack so I’ve been using @ but maybe const is just as good? Thanks.

No, you need constref then.

Michael.

Michael Van Canneyt wrote

No, you need constref then.

So for the record.... In the example given, will const make a copy of the record and constref will pass in the original record (no copy of data)?

If so, then what's the difference between constref and var? Because it sounds like they are doing the same thing - given the example.

Regards,
Graeme

In the case of const, you don't know. The compiler will do as it sees fit.

In the case of constref, you are forcing the compiler to use a reference (so no copy of data)

If so, then what's the difference between constref and var? Because it sounds like they are doing the same thing - given the example.

Behind the scenes, at an assembler level, it is using the same mechanism.

The difference is that you can assign something to a var parameter, but you cannot assign something to a constref.

Michael.

Michael Van Canneyt wrote

In the case of const, you don't know. The compiler will do as it sees fit.

Oh wow, I really didn't know that.

....snip.... The difference is that you can assign something to a var parameter, but you cannot assign something to a constref.

Thank you Michael, that was very informative information. One is never too old to learn. ;-)

Regards,
Graeme

Hi,

LCL provides the usual Delphi equivalent components like TBitBtn and TSpeedButton but there do not seem to be any glyphs to go with them.

Do I really have to make my own or are there some resources I have not found ?

Thanks.

It is actually documented:

https://www.freepascal.org/docs-html/current/ref/refsu67.html#x179-20100014.4.4

Michael.

Hi,
 
TBitBtn has property Kind, setting it to anything else than bkCustom will show the glyph (native, from widgetset).  
With TSpeedButton, you are always on your own.
 
V.
______________________________________________________________

Hi,

LCL provides the usual Delphi equivalent components like TBitBtn and TSpeedButton  but there do not seem to be any glyphs to go with them.

Do I really have to make my own or are there some resources I have not found ?

Thanks.

Oh, of course. It is longer than I realised since I've used Delphi !

For the other glyphs I guess I'll have to install one of my old D1 or D2 CDs and dig them out..

Thanks for the reminder.

Is constref compatible with Delphi?

Regards,
Marcos Douglas

Delphi has recently introduced some annotation for the same purpose.

As usual, they chose to do something different than what FPC did.

Michael.

Michael Van Canneyt wrote

It is actually documented:

I'm a step ahead. :-) Just after I sent my email, I did actually go check the documentation and read up on it. Thanks for pointing it out though.

Regards,
Graeme

Hmm, OK. Thanks.

Regards,
Marcos Douglas

Hi, LCL provides the usual Delphi equivalent components like TBitBtn and

TSpeedButton but there do not seem to be any glyphs to go with them.

Do I really have to make my own or are there some resources I have not

found ?

Lazarus/LCL questions are best asked on the lazarus mailing list ( http://lists.lazarus-ide.org/listinfo/lazarus ). While quite some of the devs there read here as well, you'll get even more feedback regarding Lazarus/LCL topics there.

Regards,
Sven

Michael Van Canneyt wrote

Delphi has recently

Huh? I thought Delphi got shut down years ago.

:?

yes, sorry. I will try to restrict questions here to fpc.

See https://www.embarcadero.com/products/delphi

Marcos Douglas

On Oct 11, 2017, at 5:01 PM, Michael Van Canneyt wrote: No, you need constref then.

Ok, so constref/var are the same in terms of copying. The docs say const reduces stack size? I never label my parameters with const but maybe it’s worth it some cases.

Regards,
Ryan Joseph

"Ryan Joseph" wrote

> On Oct 11, 2017, at 5:01 PM, Michael Van Canneyt

> > No, you need constref then. Ok, so constref/var are the same in terms of copying. The docs say const

reduces stack size? I never label my parameters with const but maybe it’s worth it some cases.

This is basically only the case for managed parameters like strings and interfaces as such don't need an implicit try...finally-block in case of const and constref to correctly reset their reference count in case of an exception

Regards,
Sven