Hi all,

I need to be able to check in a template whether the type given is an array type so that I can do some different logic. How can I do this? I would have thought that if(is(T == [])) would work, but no.


Thanks in advance

On Tuesday, 19 January 2021 at 22:26:52 UTC, Tim wrote:
> I need to be able to check in a template whether the type given is an array type so that I can do some different logic. How can I do this?

`if(is(T == E[], E))` or `isDynamicArray!T` is you `import std.traits;`

On Tuesday, 19 January 2021 at 22:26:52 UTC, Tim wrote:
> Hi all,
>
> I need to be able to check in a template whether the type given is an array type so that I can do some different logic. How can I do this? I would have thought that if(is(T == [])) would work, but no.
>
>
> Thanks in advance

You've almost got it. The correct syntax is `is(T == U[], U)`. You can read it as "there exists some type U such that T == U[]".

On Tuesday, 19 January 2021 at 22:31:47 UTC, Paul Backus wrote:
> You've almost got it. The correct syntax is `is(T == U[], U)`. You can read it as "there exists some type U such that T == U[]".

Thanks! Do I need to specify U in the template function?

On Tuesday, 19 January 2021 at 22:34:04 UTC, Tim wrote:
> On Tuesday, 19 January 2021 at 22:31:47 UTC, Paul Backus wrote:
>> You've almost got it. The correct syntax is `is(T == U[], U)`. You can read it as "there exists some type U such that T == U[]".
>
> Thanks! Do I need to specify U in the template function?

No, only inside the is(...) expression.

On Tuesday, 19 January 2021 at 22:36:47 UTC, Paul Backus wrote:
> On Tuesday, 19 January 2021 at 22:34:04 UTC, Tim wrote:
>> On Tuesday, 19 January 2021 at 22:31:47 UTC, Paul Backus wrote:
>>> You've almost got it. The correct syntax is `is(T == U[], U)`. You can read it as "there exists some type U such that T == U[]".
>>
>> Thanks! Do I need to specify U in the template function?
>
> No, only inside the is(...) expression.

What if it is a static array i.e. double[3]?

On Tuesday, 19 January 2021 at 22:38:41 UTC, Tim wrote:
> On Tuesday, 19 January 2021 at 22:36:47 UTC, Paul Backus wrote:
>> On Tuesday, 19 January 2021 at 22:34:04 UTC, Tim wrote:
>>> On Tuesday, 19 January 2021 at 22:31:47 UTC, Paul Backus wrote:
>>>> You've almost got it. The correct syntax is `is(T == U[], U)`. You can read it as "there exists some type U such that T == U[]".
>>>
>>> Thanks! Do I need to specify U in the template function?
>>
>> No, only inside the is(...) expression.
>
> What if it is a static array i.e. double[3]?

is(T == U[n], U, size_t n)

On Tuesday, 19 January 2021 at 22:45:19 UTC, Paul Backus wrote:
> On Tuesday, 19 January 2021 at 22:38:41 UTC, Tim wrote:
>> On Tuesday, 19 January 2021 at 22:36:47 UTC, Paul Backus wrote:
>>> On Tuesday, 19 January 2021 at 22:34:04 UTC, Tim wrote:
>>>> On Tuesday, 19 January 2021 at 22:31:47 UTC, Paul Backus wrote:
>>>>> You've almost got it. The correct syntax is `is(T == U[], U)`. You can read it as "there exists some type U such that T == U[]".
>>>>
>>>> Thanks! Do I need to specify U in the template function?
>>>
>>> No, only inside the is(...) expression.
>>
>> What if it is a static array i.e. double[3]?
>
> is(T == U[n], U, size_t n)

Easy, thanks a lot!