Alias template parameter to a private function

Sebastien Alaiwan via Digitalmars-d-learn digitalmars-d-learn at puremagic.com
Sat Jun 24 02:04:18 PDT 2017


Hi,

I'm trying to call std.algorithm.iteration.filter with a private 
function as a predicate.
Here's a reduced example code:

// yo.d
import std.algorithm;

void moduleEntryPoint()
{
   privateFunction1();
   privateFunction2();
}

private:

void privateFunction1()
{
   auto array = [0, 1, 2, 3, 4, 5];
   auto result = filter!isValid(array); // error: 'isValid' is 
private
}

void privateFunction2()
{
   auto array = [0, 1, 2, 3, 4, 5];
   auto result = filter!isValid(array); // error: 'isValid' is 
private
}

bool isValid(int i)
{
   return i % 2 == 0;
}

Here's the compiler output:

/usr/include/dmd/phobos/std/algorithm/iteration.d(1132): Error: 
function yo.isValid is not accessible from module iteration
yo.d(14): Error: template instance 
std.algorithm.iteration.filter!(isValid).filter!(int[]) error 
instantiating

This seems like the compiler, when instanciating the calls to 
'filter', is resolving 'isValid' from std.algorithm.iteration 
scope (however, this isn't actually the case, see below).
I was expecting this identifier to be resolved from yo.d, where 
we have access to the private functions.

Surprisingly, the following works:

void privateFunction2()
{
   static bool isValid(int i)
   {
     return i % 2 == 0;
   }

   auto array = [0, 1, 2, 3, 4, 5];
   auto result = filter!isValid(array); // error: 'isValid' is 
private
}

This makes the instanciation of 'filter' "see" 'isValid', 
however, now, the other privateFunctions can't use it.

Am I missing something here?
Thanks!



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