Switch: Case Range Syntax

[Jacob Carlborg]

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.

> 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.

-- 
/Jacob Carlborg