Hi,

I need a "new" boolean type in my applications that support three values. True, False and Null. Null value means undefined and has various uses and gets handled differently to True or False. Is this possible in Free Pascal?

Regards,
- Graeme -

_______________________________________________
fpGUI - a cross-platform Free Pascal GUI toolkit
http://opensoft.homeip.net/fpgui/

type
  TGraemeBoolean = (dbNil, dbFalse, dbTrue);

TGraemeBoolean = (gbNull, gbTrue, gbFalse);

Mattias

oh sorry, by i've missprinted prefixes:
type
 TGraemeBoolean = (gbNil, gbFalse, gbTrue);
// gb prefix stands for Greame Boolean

TGraemeBoolean = (gbNull, gbTrue, gbFalse);

imho, gbFalse should come before gbTrue.

how about that?

interface
TGraemeBoolean = (gbNull = -1, gbFalse = 0, gbTrue =1);
function dbBool(g: TGrameBoolean): Boolean; inline;
function dbAssigned(gTGrameBoolean): Boolean; inline;
implementation
function dbBool(g: TGrameBoolean): Boolean; inline;
begin
  Result := g  gbFalse;
end;
function dbAssigned(gTGrameBoolean): Boolean; inline;
begin
  Result := g  gbNil;
end;

Dope! Now why didn't I think of that. :-) Thank you very much!

Regards,
- Graeme -

_______________________________________________
fpGUI - a cross-platform Free Pascal GUI toolkit
http://opensoft.homeip.net/fpgui/

In our previous episode, Graeme Geldenhuys said:

Have a look at $packenum btw if you go that way.

Have a look at $packenum btw if you go that way.

what's the reason? i guess it's not to be used for streaming operation.

btw, is there $packsets? (for sets aligment?)

thanks,
dmitry

In our previous episode, dmitry boyarintsev said:

> Have a look at $packenum btw if you go that way. what's the reason? i guess it's not to be used for streaming operation.

Well, you never know. Shared memory is another possibility btw.

btw, is there $packsets? (for sets aligment?)

No, not that I know.

No, not that I know.

sets are always 32-bit size?

In our previous episode, dmitry boyarintsev said:

> No, not that I know. sets are always 32-bit size?

Oops I apparantly looked at outdated docs (on scenergy):

http://www.freepascal.org/docs-html/prog/progsu59.html#x66-640001.1.59

Oops I apparantly looked at outdated docs (on scenergy): http://www.freepascal.org/docs-html/prog/progsu59.html#x66-640001.1.59

Thanks so much!

Marco van de Voort wrote

Oops I apparantly looked at outdated docs (on scenergy): http://www.freepascal.org/docs-html/prog/progsu59.html#x66-640001.1.59

That documentation is not really complete. The supported settings are:
* FIXED, DEFAULT, NORMAL: the default behaviour, and behaves as described in the docs.
* 1, 2, 4: the set size depends on both the low and high value of the set element type (e.g., a set of 16..23 will be 1 byte in case of {$packset 1}), with
a) the lower bound rounded down to a multiple of the packset setting expressed in bits
b) the upper bound rounded up to 'a multiple of the packset setting (in bits)' minus 1 (e.g., 24 is a multiple of 8 bits in the above example -> -1 = 23)
c) if the set size would be 3 bytes after the above calculation, it's changed to 4 bytes
d) if the set size would be greater than 4 bytes after the above calculation, it's changed to 32 bytes.
* {$packset 8} is also supported, but kind of nonsensical in the current implementation (will always be rounded up to 32 byte, since the set size will always be > 4).

Jonas