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!

up please!

On 06/24/2017 02:04 AM, Sebastien Alaiwan wrote:

> private:
>
> void privateFunction1()
> {
>   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;
> }

A workaround is to use a lambda:

  filter!(a => isValid(a))(array)

Such limitations are pretty annoying. There were a number of similar issues in recent dmd releases. Please file a bug if it's not already there:

  https://issues.dlang.org/

Ali

On Thursday, 29 June 2017 at 20:21:13 UTC, Ali Çehreli wrote:
> A workaround is to use a lambda:
>
>   filter!(a => isValid(a))(array)

Thanks! Nice trick, this is definitely going into my company's codebase :-)

> Such limitations are pretty annoying. There were a number of similar issues in recent dmd releases. Please file a bug if it's not already there:

Thanks, will do!