Jos van Uden:
I think it's convenient, it checks for null or empty, I don't
find it confusing at all.
I agree it's shorter and it looks handy. But one of its problems
is that in D there are arrays with length zero that aren't null:
import std.stdio;
int[] foo() {
auto a = [1];
return a[0..0];
}
void main() {
if (auto data = foo()) {
writeln("here");
}
}
In the vampire code this doesn't happen because you return null
(that is represented by two zero words), but in general unlike
Python in D the safe and idiomatic way to test for array
emptiness is to use std.array.empty. Otherwise you risk having
problems.
With regards to immutablity: I do find it useful, but it
creates an anormous amount of
code clutter. So I use it only where it's really important. For
instance we have f1 and
f2, they are declared const, and then only two lines later the
constness has to be cast
away again. I find that a bit over the top.
f1 and f2 can be declared immutable, because they don't need to
change.
The later cast was a mistake of mine, I am sorry. In real-world D
code in a situation like that I do as you have done, making f1
and f2 mutable.
But on Rosettacode I think it's important to underline the
current problems in the D language itself. In an hypothetical
future version of D if you cancat two immutable arrays you should
get something that is typed as immutable, but is implicitly
castable to mutable :-)
I will think a bit more about this. Maybe I will just make f1 and
f2 mutable, it's the cleanest solution.
- "if (digits.length % 2)" instead of "if (digits.length &
1)": for the compiler they are exactly the same, because
the value is unsigned. And using a modulus is more clear here.
We are discussing about parity, not about bits.
That is a matter of opinion. If I see "% 2", my first thought
is: we're checking for even... then I realize the
"== 0" is missing.
I will add the == 0 too then.
I wrote the task myself, so I should know.
Ah :-) I didn't know. OK. So it's the Python entry to be wrong
and yours is correct.
It's fine with me. I'm glad we got rid of the ugly cast.
I agree, that cast in D was a bug of mine. (I try to fix mistakes
in your code, but once in a while my code introduces other
bugs/problems. In such cases on GitHub you can annotate code, but
on mediawiki you have to just "fix" the code. It wasn't designed
for code.)
Later I will change the code on Rosettacode.
Bye,
bearophile
