Hi all,

Is it possible to launch/spawn a thread/fibre or some other appropriate item and obtain an immutable/enum or some appropriate output at compile-time? For instance return an immutable(string) from the external thread to be used as the input to a template parameter or a CTFE function. To be clear the thread carries out run-time processing e.g. reading a file.

Thanks in advance.

On Sunday, 13 August 2017 at 07:37:15 UTC, data pulverizer wrote:
> Hi all,
>
> Is it possible to launch/spawn a thread/fibre or some other appropriate item and obtain an immutable/enum or some appropriate output at compile-time? For instance return an immutable(string) from the external thread to be used as the input to a template parameter or a CTFE function. To be clear the thread carries out run-time processing e.g. reading a file.
>
> Thanks in advance.

No, CTFE is single-threaded and additionally it is required that functions executed at compile-time are "pure", i.e. they don't affect the global state of the system and don't use any non-portable facilities. Essentially, only pure computation is allowed.

Though, specifically reading files is allowed at compile-time via the `string s = import("file.txt");` syntax, provided that the file `file.txt` is located in a directory, specified to the compiler by the `-J` flag. For more information see:
http://dlang.org/spec/expression.html#import_expressions

On Sunday, 13 August 2017 at 08:09:28 UTC, Petar Kirov [ZombineDev] wrote:
> On Sunday, 13 August 2017 at 07:37:15 UTC, data pulverizer wrote:
>> Hi all,
>>
>> Is it possible to launch/spawn a thread/fibre or some other appropriate item and obtain an immutable/enum or some appropriate output at compile-time? For instance return an immutable(string) from the external thread to be used as the input to a template parameter or a CTFE function. To be clear the thread carries out run-time processing e.g. reading a file.
>>
>> Thanks in advance.
>
> No, CTFE is single-threaded and additionally it is required that functions executed at compile-time are "pure", i.e. they don't affect the global state of the system and don't use any non-portable facilities. Essentially, only pure computation is allowed.
>
> Though, specifically reading files is allowed at compile-time via the `string s = import("file.txt");` syntax, provided that the file `file.txt` is located in a directory, specified to the compiler by the `-J` flag. For more information see:
> http://dlang.org/spec/expression.html#import_expressions

Thank you. Great explanation!