Am 21.06.2018 um 17:25 schrieb Ryan Joseph:
On Jun 21, 2018, at 10:08 PM, Sven Barth via fpc-pascal
<fpc-pascal@lists.freepascal.org> wrote:
For more questions you can start a thread in fpc-devel. That's the purpose of
that mailing list after all.
Thanks, I’ll post there tomorrow about the technical stuff.
At first glance unless I totally underestimate something it appears to be a
trivial extension to the define:= syntax but admittedly it’s edge case stuff
and probably not widely used.
I did a search and found only a few hits on the topic. Since I’ve been giving
theoretical examples here’s something more practical a user attempted. Can you
do that without macros? If I had to guess he had some funky code and just
wanted to reduce typing and copy/paste bugs.
{$define HOFFSET(rec,field) := pointer(@rec.field) - pointer(@rec)}
type
s1_t = record
a: longint;
b: single;
c: double;
end;
var
s1: s1_t;
BEGIN
s1.a := 12345;
s1.b := 1.000000001;
s1.c := 1.000000002;
writeln(HOFFSET(s1, a));
END.
The officially sanctioned way is this:
@s1_t(nil^).a
Though I do have the idea to extend the Ofs() intrinsic to handle a type
expression as well. E.g. Ofs(s1.a) returns @s1.a, but I'd like
Ofs(s1_t.a) to return @s1_t(nil^).a.
Regards,
Sven
_______________________________________________
fpc-pascal maillist - fpc-pascal@lists.freepascal.org
http://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
