Very basic questions

["Sanjay K. Agrawal" <sagrawal@cisco.com>]

Hi folks,

I am a new user to NS2. I have been struggling for past month or so to
modify
NS2 to make event based changes.

I have some very basic questions for which I didn't get satisfactory
answer 
from NS2 documentation (I have read it all). These questions are
following:

1: In tcl function always begins with code like following:
  
CBQLink instproc init { src dst bw delay q cl {lltype "DelayLink"} } {
        $self next $src $dst $bw $delay $q $lltype ; # SimpleLink ctor
        $self instvar head_ queue_ link_
        $self instvar  classifier_      ; # not found in a SimpleLink
#       $self instvar  drophead_ ; # not found in a SimpleLink

        $queue_ link $link_ ; # queue_ set by SimpleLink ctor, CBQ needs
$link_
        set classifier_ $cl

I don't understand what does the variable $self mean, what does next
mean,
I am not clear on instvar either. Does instavar make all the private
variables
accessible.

2: When I bind a variable like following in the queue.cc:

Queue::Queue() : Connector(), blocked_(0), unblock_on_resume_(1),
qh_(*this), 
	pq_(0)			/* temporarily NULL */
{
	bind("limit_", &qlim_);
	bind_bool("blocked_", &blocked_);
	bind_bool("unblock_on_resume_", &unblock_on_resume_);
	bind_bool("control_jitter_", &control_jitter_);
}

It compiles fine but give me segmentation fault when I run tcl script.
I even have the following code in ns-defaults.tcl

Queue set control_jitter_ false

In addition I don't understand the fist line of this code in queue.cc.
What are
they trying to do.

Queue::Queue() : Connector(), blocked_(0), unblock_on_resume_(1),
qh_(*this), 
	pq_(0)			/* temporarily NULL */


I know my knowledge is bit rusty, but I will appreciate your help very
much.
I have been stuck here for a while. 

Thank you in advance,

-Sanjay K. Agrawal, Cisco Systems
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