I'm confused by the following:

import std.stdio;
import std.datetime;

void main()
{
	string unitType = "seconds";
	auto seconds = 1;
//	auto myDur = dur!(unitType)(seconds); // Error unitType can't be read at compile time.
	auto myDur = dur!("seconds")(seconds); // Compiles why?
}

How is seconds able to be read at compile time but unitType cannot?

Thanks!

On Friday, 19 February 2016 at 04:08:02 UTC, Zekereth wrote:
> How is seconds able to be read at compile time but unitType cannot?

"seconds" is a literal value that the compiler knows about. unitType is a variable that might change between its declaration and use (it doesn't here, but the compiler doesn't check if it actually does, just if it *can*), so the compiler doesn't allow it.

On Friday, 19 February 2016 at 04:16:23 UTC, Adam D. Ruppe wrote:
> On Friday, 19 February 2016 at 04:08:02 UTC, Zekereth wrote:
>> How is seconds able to be read at compile time but unitType cannot?
>
> "seconds" is a literal value that the compiler knows about. unitType is a variable that might change between its declaration and use (it doesn't here, but the compiler doesn't check if it actually does, just if it *can*), so the compiler doesn't allow it.

Thanks a lot Adam!

So is there a way around this?. I want duration to be configurable at runtime.

On Friday, 19 February 2016 at 04:21:43 UTC, Zekereth wrote:
> On Friday, 19 February 2016 at 04:16:23 UTC, Adam D. Ruppe wrote:
>> On Friday, 19 February 2016 at 04:08:02 UTC, Zekereth wrote:
>>> How is seconds able to be read at compile time but unitType cannot?
>>
>> "seconds" is a literal value that the compiler knows about. unitType is a variable that might change between its declaration and use (it doesn't here, but the compiler doesn't check if it actually does, just if it *can*), so the compiler doesn't allow it.
>
> Thanks a lot Adam!
>
> So is there a way around this?. I want duration to be configurable at runtime.

Never mind I found a better solution to my problem by storing a Duration instead of the unitType. Works just fine.

Thanks a lot I appreciate your help!

On 2/18/16 11:36 PM, Zekereth wrote:
> On Friday, 19 February 2016 at 04:21:43 UTC, Zekereth wrote:
>> On Friday, 19 February 2016 at 04:16:23 UTC, Adam D. Ruppe wrote:
>>> On Friday, 19 February 2016 at 04:08:02 UTC, Zekereth wrote:
>>>> How is seconds able to be read at compile time but unitType cannot?
>>>
>>> "seconds" is a literal value that the compiler knows about. unitType
>>> is a variable that might change between its declaration and use (it
>>> doesn't here, but the compiler doesn't check if it actually does,
>>> just if it *can*), so the compiler doesn't allow it.
>>
>> Thanks a lot Adam!
>>
>> So is there a way around this?. I want duration to be configurable at
>> runtime.
>
> Never mind I found a better solution to my problem by storing a Duration
> instead of the unitType. Works just fine.
>
> Thanks a lot I appreciate your help!

Because it might help with some future issue:

Instead of auto, declare the unitType as immutable or enum:

immutable unitType = "seconds";
enum unitType = "seconds";

Then the compiler knows it won't change.

-Steve