• Mitja (36/36) Jan 10 2011 I would like to have a template which returns
• Stewart Gordon (10/16) Jan 10 2011 For what purpose? All you seem to have is a long-winded identity functi...
• Mitja (6/31) Jan 10 2011 The problem appears in the following setup:
• Simen kjaeraas (22/25) Jan 10 2011 So like this?
• Mitja (26/61) Jan 10 2011 Thanks, toDelegate is what I've been looking for.
• Stanislav Blinov (6/31) Jan 11 2011 Try it with previous compiler version. It looks like a bug I've reported...

Mitja <odtihmal gmail.com> writes:

I would like to have a template which returns
appropriate delegate, something like this:

module mod1;

import std.algorithm;
import std.array;
import std.stdio;

template DG(RT, T, F)
{
  auto DG(F fun)
  {
    RT delegate(T p)dg;
    dg = fun;
    return dg;
  }
}


void main()
{
  string[] haystack = ["item 1", "item 2", "item 3"];
  string needle = "item 2";

  auto flt = (string s){return s == needle;};

  auto dg = DG!(bool, string, typeof(flt))(flt);

  auto result = filter!(dg)(haystack);

  writeln(result);
}

The thing is I don't know what am I doing wrong here,
because sometimes works and sometimes doesn't.
For instance, if I'd added another file along with mod1.d, let's say,
mod2.d which contained:

module mod2;

import std.conv;
import std.string;
import std.random;

and compiled it like this: dmd mod2.d mod1.d, the program would produce
segmentation fault.
It works fine when packages in mod2 are omitted.

What would be the correct way for templated delegate?

Stewart Gordon <smjg_1998 yahoo.com> writes:

On 10/01/2011 13:02, Mitja wrote:
 I would like to have a template which returns
 appropriate delegate, something like this:

For what purpose?  All you seem to have is a long-winded identity function.

<snip>
 and compiled it like this: dmd mod2.d mod1.d, the program would produce
 segmentation fault.

I can't reproduce (DMD 2.051, Windows).  In what setup are you 
experiencing the problem?

 It works fine when packages in mod2 are omitted.

When which packages in mod2 are omitted?

I can only make out that this is a compiler bug that needs to be 
investigated.

 What would be the correct way for templated delegate?

It depends on what you're trying to do.

Stewart.

Mitja <odtihmal gmail.com> writes:

Stewart Gordon Wrote:

 On 10/01/2011 13:02, Mitja wrote:
 I would like to have a template which returns
 appropriate delegate, something like this:

 
 For what purpose?  All you seem to have is a long-winded identity function.
 
 <snip>
 and compiled it like this: dmd mod2.d mod1.d, the program would produce
 segmentation fault.

 
 I can't reproduce (DMD 2.051, Windows).  In what setup are you 
 experiencing the problem?

The problem appears in the following setup:

dmd is D 2.051.
As well as on Windows XP as guest OS in VirtualBox.
XP prints out: "object.Error: Access Violation"

 
 It works fine when packages in mod2 are omitted.

 
 When which packages in mod2 are omitted?
 
 I can only make out that this is a compiler bug that needs to be 
 investigated.
 
 What would be the correct way for templated delegate?

 
 It depends on what you're trying to do.
 
 Stewart.

"Simen kjaeraas" <simen.kjaras gmail.com> writes:

Mitja <odtihmal gmail.com> wrote:

 I would like to have a template which returns
 appropriate delegate, something like this:

So like this?

module mod1;

import std.algorithm;
import std.functional;
import std.stdio;

void main( ) {
   auto haystack = ["a","b","c"];
   auto needle = "b";
   auto flt = (string s){return s == needle;};
   auto dg = toDelegate( flt );
   auto result = filter!dg(haystack);
   writeln(result);
}

I would have to argue that the delegate is hardly templated, though. Not
sure what that means.

 What would be the correct way for templated delegate?

Depending on what you mean by 'templated delegate', I would say
std.functional's toDelegate, as used above.

Perhaps if you explained what you mean by 'templated delegate', I could
give a better answer.

-- 
Simen

Mitja <odtihmal gmail.com> writes:

Thanks, toDelegate is what I've been looking for.

It still segfaults, though.
The setup:
=======
module mod1;

import std.algorithm;
import std.functional;
import std.stdio;

void main( ) {
   auto haystack = ["a","b","c"];
   auto needle = "b";
   auto flt = delegate(string s){return s == needle;};
   auto dg = toDelegate( flt );
   auto result = filter!dg(haystack);
   writeln(result);
}
=========
module mod2;

import std.string;
// or import std.conv;
// or import std.random;
========
dmd mod2.d mod1.d compiles, but compiled program segfaults.

dmd is D 2.051.


Simen kjaeraas Wrote:

 Mitja <odtihmal gmail.com> wrote:
 
 I would like to have a template which returns
 appropriate delegate, something like this:

 
 So like this?
 
 module mod1;
 
 import std.algorithm;
 import std.functional;
 import std.stdio;
 
 void main( ) {
    auto haystack = ["a","b","c"];
    auto needle = "b";
    auto flt = (string s){return s == needle;};
    auto dg = toDelegate( flt );
    auto result = filter!dg(haystack);
    writeln(result);
 }
 
 I would have to argue that the delegate is hardly templated, though. Not
 sure what that means.
 
 What would be the correct way for templated delegate?

 
 Depending on what you mean by 'templated delegate', I would say
 std.functional's toDelegate, as used above.
 
 Perhaps if you explained what you mean by 'templated delegate', I could
 give a better answer.
 
 -- 
 Simen

Stanislav Blinov <blinov loniir.ru> writes:

10.01.2011 21:08, Mitja ïèøåò:
 Thanks, toDelegate is what I've been looking for.

 It still segfaults, though.
 The setup:
 =======
 module mod1;

 import std.algorithm;
 import std.functional;
 import std.stdio;

 void main( ) {
     auto haystack = ["a","b","c"];
     auto needle = "b";
     auto flt = delegate(string s){return s == needle;};
     auto dg = toDelegate( flt );
     auto result = filter!dg(haystack);
     writeln(result);
 }
 =========
 module mod2;

 import std.string;
 // or import std.conv;
 // or import std.random;
 ========
 dmd mod2.d mod1.d compiles, but compiled program segfaults.

 dmd is D 2.051.

Try it with previous compiler version. It looks like a bug I've reported 
not so long ago: in 2.051 functions with 'auto' result type and at least 
one parameter cause segfault during compilation when they are in a 
separate module. I can't remember issue number right now (and have no 
internet connection to find it), but it's pretty recent.