On 2011-08-18 15:36, Andrei Alexandrescu wrote:
On 8/18/11 6:42 AM, Jacob Carlborg wrote:
On 2011-08-18 00:51, Andrei Alexandrescu wrote:
On 8/17/11 2:35 PM, Jacob Carlborg wrote:
D should have a built-in range type. One that supports syntax for both
including and excluding the last element:
auto a = 3 .. 5
auto b = 3 ... 5
Then we wouldn't need a special range syntax for switch statements. You
could store ranges in variables and pass them to functions. opSlice
probably wouldn't be needed, instead opIndex could be used and you
would
declare the method to take a range instead of two integers.
I doubt that would work well. Let's ignore for now mundane issues such
as the ambiguity of 3...5 and focus on something like:
I'm just hoping that floating point syntax will be removed. I know a lot
of people agree with me on this.
int x;
...
switch (x) {
case 3 ... 5: return 1;
default: return 0;
}
We'd need to change the behavior of switch anyway, or we'd need to
define equality such that e.g. 4 == 3 ... 5. But then equality is not
transitive anymore because 4 == 2 ... 6 too, but 3 ... 5 is not equal to
2 ... 6.
There could be some kind of "include" function/property or similar. Just
as there are built-in properties on other types in D.
There could be indeed a lot of things. My point is that there _need_ to
be such. It's not a simple, minute addition.
Adding new built-in types is not easy. For a variety of reasons we
should move the other way (per e.g. the hashtables discussion
elsethread).
Andrei
I know that the implementation of the associative arrays have been moved
to the runtime, if you're referring to that. But the compiler still
knows about the associative array, right? I don't care where a range
type would be implemented, in the compiler or in the runtime.
I'm not talking about an implementation difficulty, but about semantics
difficulties within the language. My point is that although the feature
superficially looks easy to add and nice to have, in reality there are a
lot of subtle additional changes we must make to the language semantics.
Andrei
Ok, we can stop this discussion. In my original post I was just trying
to say that it's a pity that D doesn't have a built-in range type and if
it was three, four years ago it could have been added to the language,
perhaps. I could have avoided a few, in my opinion, "hacks", like the
case ranges. I fully understand if this feature cannot be added to the
language now.
--
/Jacob Carlborg
