boost.coroutine vs my $generator.

Today I saw discussion about boost.coroutine on gmane:

Generators and coroutines are conceptually the same feature and I have implementation of $generator thing that can be used to implement coroutines.

My implementation is of 15 lines of code and does not require any threads/fibers and so context switches – pure C++ with macro magic, pretty straightforward though.

Anyway, here is an example how coroutine can be implemented using that $generator thing.
First, let’s define coroutine (or generator) that will establish connection with some server and will supply (yield) data chunks read from socket:

$generator(net_reader)
{
   socket_t     sock;
   byte         buffer[2048];

   net_reader(const char* addr) { sock.connect(addr); }
   
   // from $emit to $stop is a body of our coroutine:
    
   $emit(slice<byte>) // Coroutine will emit slice<byte> values. Start of coroutine body.

      while( sock.valid() )
      {
          slice<byte> r(buffer,0);
          r.length = sock.read(buffer,sizeof(buffer));
          if(r.length)
            $yield( r ); 
          else 
            break; 
      }

   $stop; // stop. End of coroutine body.
};

Having this we can write code that will read data chunk by chunk and store it in some array.

array<byte> data;
net_reader  get("data.example.com:4002");

for(slice<byte> chunk; get(chunk);)
  data.push(chunk);

That’s easy, no?

Yes, $generator thing is not free from problems (e.g. you cannot use switch() inside its body) but other than that and in 99% of coroutine cases you will get what is needed from generators/coroutines. And without those tons of code.