There is a fair bit of range related code in the standard library structured like:

    auto MyRange(Range)(Range r)
        if (isInputRange!Range)
     {
        static struct Result
        {
            private Range source;
            // define empty, front, popFront, etc
        }
        return Result(r);
    }

I'm curious about what declaring the Result struct as 'static' does, and if there are use cases where it be better to exclude the static qualifier.

--Jon

V Wed, 09 Dec 2015 21:10:43 +0000
Jon D via Digitalmars-d-learn <digitalmars-d-learn@puremagic.com>
napsáno:

> There is a fair bit of range related code in the standard library structured like:
> 
>      auto MyRange(Range)(Range r)
>          if (isInputRange!Range)
>       {
>          static struct Result
>          {
>              private Range source;
>              // define empty, front, popFront, etc
>          }
>          return Result(r);
>      }
> 
> I'm curious about what declaring the Result struct as 'static' does, and if there are use cases where it be better to exclude the static qualifier.
> 
> --Jon

It make it non-nested struct: https://dlang.org/spec/struct.html#nested

On Wednesday, 9 December 2015 at 21:23:03 UTC, Daniel Kozák wrote:
> V Wed, 09 Dec 2015 21:10:43 +0000
> Jon D via Digitalmars-d-learn <digitalmars-d-learn@puremagic.com>
> napsáno:
>
>> There is a fair bit of range related code in the standard library structured like:
>> 
>>      auto MyRange(Range)(Range r)
>>          if (isInputRange!Range)
>>       {
>>          static struct Result
>>          {
>>              private Range source;
>>              // define empty, front, popFront, etc
>>          }
>>          return Result(r);
>>      }
>> 
>> I'm curious about what declaring the Result struct as 'static' does, and if there are use cases where it be better to exclude the static qualifier.
>> 
>> --Jon
>
> It make it non-nested struct: https://dlang.org/spec/struct.html#nested

Thanks. So, is in the example above, would the advantage be that 'static' avoids saving the enclosing state, which is not needed?

Yes, exactly. Some people even use static if it is not needed because it is
harmless. And remove it only when enclosing context is demand.
Dne 9. 12. 2015 22:40 napsal uživatel "Jon D via Digitalmars-d-learn" <
digitalmars-d-learn@puremagic.com>:

> On Wednesday, 9 December 2015 at 21:23:03 UTC, Daniel Kozák wrote:
>
>> V Wed, 09 Dec 2015 21:10:43 +0000
>> Jon D via Digitalmars-d-learn <digitalmars-d-learn@puremagic.com>
>> napsáno:
>>
>> There is a fair bit of range related code in the standard library
>>> structured like:
>>>
>>>      auto MyRange(Range)(Range r)
>>>          if (isInputRange!Range)
>>>       {
>>>          static struct Result
>>>          {
>>>              private Range source;
>>>              // define empty, front, popFront, etc
>>>          }
>>>          return Result(r);
>>>      }
>>>
>>> I'm curious about what declaring the Result struct as 'static' does, and if there are use cases where it be better to exclude the static qualifier.
>>>
>>> --Jon
>>>
>>
>> It make it non-nested struct: https://dlang.org/spec/struct.html#nested
>>
>
> Thanks. So, is in the example above, would the advantage be that 'static' avoids saving the enclosing state, which is not needed?
>