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digitalmars.D.learn - Launch and obtain thread output during compile time

reply data pulverizer <data.pulverizer gmail.com> writes:
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.
Aug 13
parent reply Petar Kirov [ZombineDev] <petar.p.kirov gmail.com> writes:
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
Aug 13
parent data pulverizer <data.pulverizer gmail.com> writes:
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!
Aug 13