Can messages be sent to processes interactively?

[Torbjorn Tornkvist]

> Yes, I did not realize that server functions always need to be exported. I
> see now that spawm() always returns a pid even when the arguments are
> nonsensical:  spawn(mud, mud, []).  But everything works fine now and I'm
> happily writing concurrent code.

A little helpful comment here: 

Think of spawn/3 as:

 1. Create a new (empty) erlang process.
 2. Perform an apply/3 in the new process.
 
To be able to do the apply/3 you have to export the M:F/A.

Another little comment: It is very instructive to make
use of the debugger, especially when you write concurrent code.
To use it do the following from your erlang shell prompt;

1> ii(YOUR-MUDULE-NAME).

2> iaa(init).

3> YOUR-MODULE-NAME:foo(....).

A window will now pop-up the first time you execute
the debugged (interpreted) code. From here: singe-step,
inspect variables, etc...

Another useful command is: im().
It will bring up a monitor window displaying all
processes currently being debugged. Attach yourself
to a process by double-click on one of the lines (in the
displayed matrix) representing the process.

Finally: ib(YOUR-MODULE-NAME, LINE-NO).
Sets a break point in a module. By using: iaa(break)
the window will now pop-up when you hit the break point.

All of this can of course be done from the menues of
the monitor window, but the command interface I have 
showed here is much faster and easier to use (IMHO... ;-).

/Tobbe