On Thursday, 25 September 2014 at 23:08:53 UTC, SlomoTheBrave
wrote:
a way around this is not to use anySatisfy nor the template,
for example this works as expected:
[...]
My problem is that in this example, attributes are in the same
order as the parameter. But this come from a code generator,
which takes class defined by the user, so I have to assume they
might not be in the correct order :)
which is less abstruse. However I don't know if it has hurted
your eyes too but the output lines order shows there is a
problem too:
Current attr is: p1
Instantiated for: p1
Instantiated for: p2
Instantiated for: p3
Current attr is: p2
Current attr is: P3
instead of
Current attr is: p1
Instantiated for: p1
Current attr is: p2
Instantiated for: p2
Current attr is: P3
Instantiated for: p3
o!o
On Thursday, 25 September 2014 at 23:37:11 UTC, Ali Çehreli wrote:
Surprisingly, that indicates that anySatisfy did instantiate
CmpName with all three string values, meaning that perhaps we
don't have shortcut behavior for 'bool' eponymous templates.
This is documented
(http://dlang.org/phobos/std_typetuple.html#.anySatisfy):
Evaluation is *not* short-circuited if a true result is
encountered; the template predicate must be instantiable with all
the given items.
When I use myAnySatisfy instead of anySatisfy, I see that I am
right: The last expression above does not stop instantiating
after "p1". In other words, even though myAnySatisfy!(F, T[$/2
.. $ ] is unnecessary (because the first part of || is already
'true'), it gets instantiated anyway.
[...]
This looks like an enhancement request.
Ali
I didn't consider this aspect, and there's definitely ground for
optimization. However, let's say I replace the definition of
MyClass with:
----
class MyClass {
@(UDAStruct("p3"), UDAStruct("P2"), UDAStruct("p1")) // P2 is
a typo
void func(int p1, string p2, float p3) {}
}
----
In this case, anySatisfy is right to instantiate all 3 templates
on the first iteration. Here's the result:
----
$ dmd -unittest -run bug.d
Current attr is: p3
Instantiated for: p1
Instantiated for: p2
Instantiated for: p3
Current attr is: P2
Current attr is: p1
----
There is no needless instantiation in this case, yet we still
have the same behaviour (static assert not triggered).
