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digitalmars.D.learn - Alias template parameter to a private function

reply Sebastien Alaiwan <ace17 free.fr> writes:
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!
Jun 24
next sibling parent Sebastien Alaiwan <ace17 free.fr> writes:
up please!
Jun 29
prev sibling parent reply =?UTF-8?Q?Ali_=c3=87ehreli?= <acehreli yahoo.com> writes:
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
Jun 29
parent Sebastien Alaiwan <ace17 free.fr> writes:
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!
Jun 29