So the discussions about Attributes and Aspect Oriented Programming (AOP) got me thinking... Basically AOP requires injecting code fragments together in a comprehensible way. Similarly, Attributes that go beyond @note (such as @GC.NoScan) need similar ability.

D already has the ability to mixin arbitrary code fragments at compile time, and to process those in useful ways through CTFE. Which rocks. What it lacks is the ability to reflect upon the actual source code due to IO limitations of CTFE. So creating a mixin templates which pieces together a unique object is, to my knowledge, currently next to impossible (and slow since you'd have to parse and isolate code in .d file multiple times in a separate process, then compile again to put it all together).

So, to quote Walter, what compelling features would it bring? Here's an example of a simple AOP program from the AOP wiki page (probably not the best implementation, but the concept is there):

  struct BankType
  {
    void transfer() { ... }
    void getMoneyBack() { ... }
  }

  struct Logger
  {
    void transfer() {
      log("transferring money...");
    }
    void getMoneyBack() {
      log("User requested money back");
    }
  }

and now some magic...

  string bankCode(T...)(T aspects) {
    auto code = "struct Bank {";
    auto members = [__traits(allMembers, Bank)];
    foreach (m; members) {
      code ~= "void "~m~"() {";
      code ~= __traits(getMember, Bank, m).codeof;
      foreach (a; aspects) {
        if (__traits(hasMember, a, m) {
          code ~= __traits(getMember, a, m).codeof;
        }
      }
      code ~= "}"
    }
    return code ~ "}";
  }

  mixin template Bank(T...)
  {
    mixin(bankCode(T));
  }

  mixin Bank!Logger;

  void main() {
    auto b = Bank();
    b.transfer(); // logs
    b.getMoneyBack(); // ditto
  }

So this would allow us to make "Compilers" within the Compiler (Codeception), since we could parse/strip/append any existing code fragments together in endless combination. Generic "Builders" could probably be built and put into a std.builder lib for general use.

One particular use I have in mind is for Behavior Objects (Game Scripts). Each behavior would hold Property(T) objects which define per-property, per-state "binding" dependencies (eg. position.x.bind(other.x, State.Idle)) and execution code. On release, the Property(T) object would be stripped away (leaving just T) and it's behavior code "compressed" with others into optimized functions.

I don't know much about the internals of DMD, so I'm not sure this is a realistic request, but I think the idea is compelling. Also, for Attributes I'm not sure this technique is really applicable. But it's possible that the compiler could exploit this internally for certain Attributes like @GC.whatever

ps. Mono-C#'s NRefactory, and Microsoft .Net's forthcoming Roslyn Project are the only comparable infrastructures I can think of with this level of reflection, and they're the foundation to some pretty innovative new development tools.

NRefactory: http://wiki.sharpdevelop.net/NRefactory.ashx
Roslyn: http://msdn.microsoft.com/en-us/vstudio/hh500769

On Thursday, 22 March 2012 at 16:55:34 UTC, F i L wrote:
> ps. Mono-C#'s NRefactory, and Microsoft .Net's forthcoming Roslyn Project are the only comparable infrastructures I can think of with this level of reflection, and they're the foundation to some pretty innovative new development tools.
>
> NRefactory: http://wiki.sharpdevelop.net/NRefactory.ashx
> Roslyn: http://msdn.microsoft.com/en-us/vstudio/hh500769

Even if I'm closer to the opposite of a MS-evangelist... color me impressed, I like your idea. +1.

in addition to .codeof, let's think about .astof returning an abstract syntax tree.

On Thursday, 22 March 2012 at 18:06:24 UTC, Felix Hufnagel wrote:
> in addition to .codeof, let's think about .astof returning an abstract syntax tree.

I agree, as stated on the IRC, .astof (and therefor .astof.toString()) is a much better concept.

On Thursday, 22 March 2012 at 18:06:24 UTC, Felix Hufnagel wrote:
> in addition to .codeof, let's think about .astof returning an abstract syntax tree.

I haven't really looked at DMD's AST structure, but I assume we could just duplicate that minus any CTFE stuff or codegen stuff.

Am 22.03.2012 19:06, schrieb Felix Hufnagel:
> in addition to .codeof, let's think about .astof returning an abstract
> syntax tree.

Would this not require something similar to the expression trees in .NET?

http://msdn.microsoft.com/en-us/library/bb397951.aspx

--
Paulo

Am 22.03.2012 18:34, schrieb CTFE-4-the-win:
> On Thursday, 22 March 2012 at 16:55:34 UTC, F i L wrote:
>> ps. Mono-C#'s NRefactory, and Microsoft .Net's forthcoming Roslyn
>> Project are the only comparable infrastructures I can think of with
>> this level of reflection, and they're the foundation to some pretty
>> innovative new development tools.
>>
>> NRefactory: http://wiki.sharpdevelop.net/NRefactory.ashx
>> Roslyn: http://msdn.microsoft.com/en-us/vstudio/hh500769
>
> Even if I'm closer to the opposite of a MS-evangelist... color me
> impressed, I like your idea. +1.
>

Same here.

Microsoft R&D does lots of cool stuff actually, pity that sometimes they
get it so wrong, due to the way the management/marketing works.


--
Paulo

On 03/22/2012 07:08 PM, F i L wrote:
> On Thursday, 22 March 2012 at 18:06:24 UTC, Felix Hufnagel wrote:
>> in addition to .codeof, let's think about .astof returning an abstract
>> syntax tree.
>
> I agree, as stated on the IRC, .astof (and therefor .astof.toString())
> is a much better concept.

I think that would necessitate the addition of AST macros.

Timon Gehr wrote:
> I think that would necessitate the addition of AST macros.

You mean passing DMD's actual AST tree object? Only a stripped down version?