ipbitch!

[Eddie Kohler]

The language is ready. It even has nice error messages because I like
wasting my time. I've checked in everything including a simple (broken)
`sample.ipb' file so you can see error messages. To run a driver from the
language, make a file `xxx.ipb' and run:

	  % make ed && ./ed xxx.ipb

HOW TO WRITE A LANGUAGE-READY FACTION:

1. Have a nullary constructor (no arguments).

2. Constructors shouldn't do anything except set data members. Instead...

3. Put all initialization processing in the
   `int initialize(ErrorHandler *)'
   method. This method should return 0 on success, -1 on failure. Please
   don't call `exit()'; just return -1, and leave it to the Router object
   to propagate the failure. See LiveReader and LiveWriter for examples.

4. Call methods on the `ErrorHandler *' object if there is an error. Do not
   call fprintf. Again, see LiveReader and LiveWriter for examples.

5. Write a
   `FACTION_SUBTYPE * clone() const'
   method which returns a copy of the current faction. Please try to copy
   any configuration info into the clone. In other words, I want these two
   sequences of operations to have equivalent results:

       ComplexFaction *f1 = new ComplexFaction;
       f1->configure("blah blah blah");
       ComplexFaction *f2 = f1->clone();
   -and-
       ComplexFaction *f1 = new ComplexFaction;
       f1->configure("blah blah blah");
       ComplexFaction *f2 = new ComplexFaction;
       f2->configure("blah blah blah");

6. THE HARD PART: Write a
   `int configure(const String &, ErrorHandler *)'
   method which configures your faction dynamically from a string. I have
   added this method to a couple of the existing factions (Strip,
   TimedSource, TimedSink, LiveReader, LiveWriter). The problem of course
   is parsing the string. The functions in `confparse.hh' may be helpful.
   I will add more functions there as it becomes clear what we need.

HOW FACTIONS ARE CREATED

1. Find `ftype', which is a representative of the faction type (so a Strip,
   say)
2. Set	`f = ftype->clone()'. `f' is the actual faction object
3. Call `f->configure(configuration_string, error_handler)'
4. Analyze personalities (check push & pull)
5. Call `f->assign_personality(personality)' if `f' was agnostic
6. Check that the inputs & outputs are all valid.
   This includes creating any inputs & outputs actually used by
   factions with unlimited inputs & outputs.
7. Call `f->initialize(error_handler)'
8. All done!

love,
ed