On Monday, 17 December 2012 at 15:46:22 UTC, anonymous wrote:
On Monday, 17 December 2012 at 15:10:24 UTC, js.mdnq wrote:
This i probably a rather dumb question but I've been up all
night and therefor have a really good excuse ;) (I can barely
see straight...)
Is opGet the reverse opAssign? I can't find any docs on it but
it does let me write converters from my type to another type.
e.g.,
struct X { int value; }
double x = xX;
without an opGet or alias this I get an error about not being
able to implicitly convert. Using alias this solves the
problem. Using opGet seems to let me write a converter(which I
can't seem to do otherwise).
For example, it seems I could use opGet to normalize X's value
when converting to a double.
That is, the way I see it is
double x = xX;
The compiler checks to see if double has an opAssign that will
convert X to a double. If not it checks if X has an opGet
call(a sort of reverse opAssign).
Is this the correct understanding of opGet or is there more
too it.
What if I have
struct X { int value; X opAssign(Y y); }
struct Y { double value; X opGet(); alias opGet this; }
"opGet" is not a special name. The magic comes from alias this.
You can use another name just fine.
Thanks, that makes sense... no wonder I couldn't find it.
then
X x; Y y;
what does
x = y;
y = x;
do?
It seems the first will call X's opAssign and Y's opGet unless
there is precedence?
I guess opAssign wins, because alias this is only considered if
it doesn't work out with the original type.
That might be ok because chances are X will not have an opAssign
for Y anyways as long as opGet is not called first. Hence opGet
should only be called which is what I want. I guess the real
problem is that if X does know about Y and has an opAssign for it
then there is trouble because opAssign might not convert the
value the way I want it to(which is why I'm using opGet).
y = x will fail with the implicit conversion error?
Yes, assigning x directly to y doesn't work, and assigning it
to y.opGet (via alias this) doesn't work either, so it fails.
Thanks
