[Submission] D Slices

[Nick Sabalausky]

"eles" <eles at eles.com> wrote in message 
news:is2qgc$2o7h$1 at digitalmars.com...
>> The right boundary of a slice is exclusive.
>
> I think it should be stated more obvious in the paper.
>
>> This makes sense, so you can
>> do stuff like a[1..$] (== a[1..a.length]) to get a slice that
> contains
>> all elements of a except for the first one (a[0]).
>
> I disagree, but I have not much influence here, although I will
> defend my point of view. I find it quite unpleasant to remember which
> of the left and right bounds are exclusive and, moreover, this
> precludes slicing with a[i1..i2] where i1 and i2 are only known at
> the runtime and may be i2<i1 (and not necessarily i1<i2).
>

When I first started with D, ages ago, I was skeptical about the half-open 
slices. It sounded unbalanced. But since then, I've been won over by it for 
a few reasons (in no particular order):

1. After years of using D, I've never had a problem with it working that 
way. And even initially, I found it very easy to learn and get used to it.

2. I've found it easier to avoid off-by-one errors. I don't have to think 
about them as much.

3. arr[a..b].length == b-a     <-- That's a *very* nice, clean, useful 
property to have. And I think it's one of the main reasons for #2 above. In 
fact, this actually makes it feel more balanced to me than having inclusive 
on both ends.

4. The following:

string str = "ABCDEF";
int splitIndex = 3;

string part1 = str[0 .. splitIndex];
string part2 = str[splitIndex .. $];

assert(part1 ~ part2 == str);

Ie, when you split an array, you can use the same index for both halves. No 
"+1"-ing. It just works. Don't have to think about it.