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hello EmacsConf
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thanks very much first of all to the
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organizers of the conference
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and to the audience who I hope is out
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there somewhere
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uh for giving me this chance to talk
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about Emacs and some of my uh
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my poking around with Emacs lisp my name
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is eric abrahamson I'm not
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a professional programmer but I use
0:00:20.960,0:00:24.800
Emacs all day
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every day for writing for translating
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for project management
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and most importantly for email which
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will be the
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subject of my talk today so I'm talking
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about object-oriented code in Emacs
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uh most famous possibly oldest
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definitely most notorious news reader
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slash Emacs client
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email client so in particular object
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oriented code
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in news why object-oriented code
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the way news works is it started off as
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a news reader so for access
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accessing nntp servers and later on grew
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a whole bunch of new functionality as a
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mail client so it can talk to imap
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servers
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mail dealer directories uh folders on
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your file system all kinds of stuff
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but it presents a unified interface to
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all those things so it's basically
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polymorphism
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one of the the basic fundamental
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principles of object oriented code so
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it's a good fit second reason is it
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already is
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object oriented and I'll get into what
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that means
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in a second so
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the background that you should know is
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that most of this code was written in
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the 90s
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Emacs lisp has only grown sort of
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official
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object orientation support libraries
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over the past 10 years or so
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from about 2010 to the present so what
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does
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news do so the basics of
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object orientation in most languages are
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you you define
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a class of some sort and then you
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instantiate that class and these
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class instances have two things they
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have data attributes or
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slots or members or whatever you're
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going to call them and they have
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methods which operate on individual
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instances
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so you could say that you create or
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instantiate an instance of a class in
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that instance
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owns two things that owns its set of
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attributes
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and it owns some methods which
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also work on the on the instance
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so both in nurse's existing code and in
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the more standard object oriented Emacs
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lisp libraries
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this relationship is turned on its head
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a little bit
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in that data slots and
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uh and instance methods are defined
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outside of the
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class or the instances themselves so
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they are top level definitions
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so we'll get to what that means in the
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in the newer libraries um
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in a bit but uh first I want to talk
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about how news does this and in order to
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do that we are going to go deep into
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the darkest corner of the new co source
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code tree to a library called
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nno.l very cryptically
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titled uh library and when we open it up
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we find
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a library with no code comments and
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almost no doc strings
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almost as if lars was a little ashamed
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not ashamed but knew he was doing
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something a little bit crazy
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and didn't want anyone to see so
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this file contains the the object
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oriented mechanism
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whereby you can define different kinds
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of back ends for news
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and then those back ends can be
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instantiated as individual
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servers and as you define these backends
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you're supposed to use
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two macros which you can see here one is
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called def
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vu and one is called defu and if you
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look at the definitions the definitions
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look pretty simple here def vu basically
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turns into a def var
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and foo turns into a defund
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and along with those basic definitions
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the library also does some registration
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memoization caching of those variables
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it saves them in the structure
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for later use so that we know that those
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are meant to be
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uh attributes and methods that are used
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with instances
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with server instances but you can see
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that there's no server instance
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definition here there's no
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like no nothing these are top level
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these are top level
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definitions so really data attributes
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for
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new servers and
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methods or functions that operate on
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those instances are completely
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separate mechanisms they don't really
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have anything to do with each other they
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don't belong to the same data structures
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so how do they work follow me
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aka methods and attributes these are all
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the things I just said
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so when you define a
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a backend type
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in noose what you get is this a
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definition a list
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and it'll say there is such a back end
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as nnml
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and these are its uh data attributes
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that any
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given instance can have and then these
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are
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the functions or methods that are
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defined to operate on
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an instance of this backend so a server
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that belongs to the nnml
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backend so at least we have this data
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here so that's that's handy we don't you
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don't really touch that that's like very
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very very deep
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um use code that doesn't really come up
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even as a
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even as a bug squasher or whatever we
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don't touch that very often but there
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they are and that's
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that's how they work now the next thing
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that obviously you want to know is okay
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where are if I've started up news where
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are my servers
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uh where are these server objects since
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this is object oriented
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programming and the weird thing that you
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will eventually
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figure out in some cases after years of
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poking around in the new source code
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is that servers do not exist in an
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ontological
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philosophical sense as objects the
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primary data structures of noose are
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groups
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and in sort of an object-oriented
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hierarchical you know mindset you'd
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think well
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groups belong to servers so servers must
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exist but they don't
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each group and here you can see some
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examples of groups
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these are basically the data structures
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that represent a group each group also
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has a little entry here that
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that tells you what server it belongs to
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and each group
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replicates that data uh saying which
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server it belongs to and so when
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nurse is going through doing its
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business uh trying to figure out what's
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like updating mail from the groups or
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whatever almost every time
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it will cycle through all the list of
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groups it'll
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it'll look at all the server definitions
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and it will categorize the groups by
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server
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which which is just weird because you're
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sort of looking for okay where does the
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server exist it doesn't exist it's put
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together
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every time uh out of out of code
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elsewhere in the news code base
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specifically from these group
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these group definitions and so this is
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very odd because
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in in some sense like here this one its
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server is
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nnml and an empty string so there's a
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certain sense here in which this server
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is not
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really an object at all what it is is a
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set of instructions for how to find
0:07:07.759,0:07:11.199
messages
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and this set of instructions is go to
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the default place where the user
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might have their mail and expect to find
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messages
0:07:16.000,0:07:19.840
there in an nml format which is
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basically just one message per
0:07:19.840,0:07:23.840
um per file and any number of groups
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could have those same instructions uh
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but they're not it's not really a thing
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it's really just a
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it's more of a procedural instruction
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and on the other end of the spectrum you
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might have an nni map
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server which very much is a thing it has
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its own it has its own server its own
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port its own authentication
0:07:37.759,0:07:41.360
system so some of the servers are more
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like things some of the servers are more
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like instructions
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as news works right now um these
0:07:45.520,0:07:48.879
most of the servers are treated like
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just instruction sets
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and and there's no place where you can
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go and find them there's no one central
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uh variable that defines them all so how
0:07:55.360,0:07:57.520
do the
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um so we'll talk about the methods in a
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second how do the data attributes work
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uh put very crudely um
0:08:02.639,0:08:05.919
your servers when they're put together
0:08:04.479,0:08:08.080
uh they are okay they are
0:08:05.919,0:08:08.960
kept in a variable and it's called nno
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nno
0:08:08.960,0:08:12.960
state a list and there's a concept to
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this of the current server
0:08:12.960,0:08:19.039
so when we go here let's go back to
0:08:16.560,0:08:20.560
our nnno definition a list so when we
0:08:19.039,0:08:22.240
have an nnml
0:08:20.560,0:08:24.400
server say we have one here and it's
0:08:22.240,0:08:26.639
just this blank string
0:08:24.400,0:08:28.879
these are all when you define that in
0:08:26.639,0:08:31.919
your own uh server definition code
0:08:28.879,0:08:32.399
you can put in different values for all
0:08:31.919,0:08:35.760
of these
0:08:32.399,0:08:37.039
various attributes and when noose comes
0:08:35.760,0:08:38.959
when it comes time for news to operate
0:08:37.039,0:08:40.640
on this server in particular ask it to
0:08:38.959,0:08:42.080
you know open a group or get new mail
0:08:40.640,0:08:45.360
what it will do is it will take
0:08:42.080,0:08:45.920
that particular server's data from these
0:08:45.360,0:08:47.600
symbols
0:08:45.920,0:08:49.600
and it will copy all that information
0:08:47.600,0:08:51.760
into the global devfars
0:08:49.600,0:08:53.120
so for the time that you are operating
0:08:51.760,0:08:55.920
on this particular server
0:08:53.120,0:08:56.800
its individual data becomes the values
0:08:55.920,0:08:59.360
of these global
0:08:56.800,0:09:00.560
variables which when you realize what's
0:08:59.360,0:09:02.080
happening is sort of terrifying you
0:09:00.560,0:09:04.480
think oh my god
0:09:02.080,0:09:05.760
but at the same time it's actually kind
0:09:04.480,0:09:07.279
of impressive and it's amazing that it
0:09:05.760,0:09:09.120
works as well as it does
0:09:07.279,0:09:10.880
I'm actually a little bit in awe of the
0:09:09.120,0:09:12.560
of the code in this in this library I
0:09:10.880,0:09:15.760
think it's pretty impressive
0:09:12.560,0:09:18.320
so as you nno change server
0:09:15.760,0:09:20.080
uh this function here these values get
0:09:18.320,0:09:21.440
copied into the global value into the
0:09:20.080,0:09:22.399
global variables and then as you go on
0:09:21.440,0:09:24.000
the next server
0:09:22.399,0:09:26.399
that gets you know cleaned out and
0:09:24.000,0:09:29.680
recopied there are a few
0:09:26.399,0:09:32.000
um a few other slot types
0:09:29.680,0:09:33.440
or attribute types which do because all
0:09:32.000,0:09:34.720
of these attributes see they all start
0:09:33.440,0:09:37.920
with the nml
0:09:34.720,0:09:40.560
or in this case and in folder prefix
0:09:37.920,0:09:41.760
but there are a few slot types that all
0:09:40.560,0:09:43.279
servers need for
0:09:41.760,0:09:45.920
for instance their most recent status
0:09:43.279,0:09:46.640
message a status symbol like open denied
0:09:45.920,0:09:48.080
whatever
0:09:46.640,0:09:49.680
and that data is sort of scattered
0:09:48.080,0:09:51.200
around the rest of the news
0:09:49.680,0:09:53.440
code base in various variables or
0:09:51.200,0:09:55.440
various places
0:09:53.440,0:09:56.560
so that's that sort of just contributes
0:09:55.440,0:09:57.360
to the confusion when you're trying to
0:09:56.560,0:10:00.720
figure out why
0:09:57.360,0:10:03.839
things are going wrong so that is our
0:10:00.720,0:10:05.440
um nnoo which is and
0:10:03.839,0:10:07.360
sort of how the attributes and these
0:10:05.440,0:10:09.120
global variables work
0:10:07.360,0:10:10.480
if we want to talk about defu and the
0:10:09.120,0:10:19.839
methods we
0:10:10.480,0:10:19.839
go to
0:10:20.800,0:10:25.600
and so this is the place where all the
0:10:23.200,0:10:27.200
server level methods are defined
0:10:25.600,0:10:29.279
and what we have here are things like
0:10:27.200,0:10:32.640
here's an example there's closed server
0:10:29.279,0:10:36.320
this closed server is given a
0:10:32.640,0:10:38.079
a server as a an argument
0:10:36.320,0:10:40.560
it looks at the server and basically it
0:10:38.079,0:10:42.079
finds the proper function to call on
0:10:40.560,0:10:45.120
this particular server
0:10:42.079,0:10:45.600
using the function new skip function by
0:10:45.120,0:10:48.959
taking
0:10:45.600,0:10:49.760
the sort of latter half of this function
0:10:48.959,0:10:52.079
symbol
0:10:49.760,0:10:53.440
and pasting it together with the symbol
0:10:52.079,0:10:56.800
that represents the back end so
0:10:53.440,0:10:59.600
if you were calling this on an nni map
0:10:56.800,0:11:01.279
server your skip function would look at
0:10:59.600,0:11:02.240
your imap server look at closed server I
0:11:01.279,0:11:05.120
knew what
0:11:02.240,0:11:05.120
it would come up with
0:11:07.839,0:11:11.920
server sure enough there's an imac close
0:11:10.240,0:11:12.240
server and it'll call this code and then
0:11:11.920,0:11:14.000
it'll
0:11:12.240,0:11:15.279
it'll go and do its other bookkeeping
0:11:14.000,0:11:18.320
another sort of
0:11:15.279,0:11:19.279
surrounding code and so that's not that
0:11:18.320,0:11:22.640
actually works pretty well
0:11:19.279,0:11:24.959
uh as as things go uh defu
0:11:22.640,0:11:26.800
makes a record that this this function
0:11:24.959,0:11:28.320
exists and nus gets function get
0:11:26.800,0:11:29.600
function looks on that cache finds the
0:11:28.320,0:11:30.959
function and calls it
0:11:29.600,0:11:32.560
now what's particularly confusing is
0:11:30.959,0:11:33.360
that you don't actually even have to use
0:11:32.560,0:11:35.519
defu
0:11:33.360,0:11:38.399
so whoever wrote and then mail gear
0:11:35.519,0:11:39.920
which is a weird library
0:11:38.399,0:11:41.600
said to heck with you I'm not using any
0:11:39.920,0:11:43.120
of these
0:11:41.600,0:11:45.839
any of this machinery I'm going to do it
0:11:43.120,0:11:49.680
myself so we have
0:11:45.839,0:11:52.320
def structs to hold uh the instance
0:11:49.680,0:11:53.040
data and then we have just plain old
0:11:52.320,0:11:55.680
defense
0:11:53.040,0:11:57.279
for things like animal your close server
0:11:55.680,0:11:59.279
request close all of these
0:11:57.279,0:12:00.320
these server level uh variables and it
0:11:59.279,0:12:03.360
just turns out that
0:12:00.320,0:12:05.839
news in its belt and suspenders
0:12:03.360,0:12:07.279
approach to uh to coding it'll actually
0:12:05.839,0:12:10.320
just go out if it can't find
0:12:07.279,0:12:12.160
the memoized function it'll just go out
0:12:10.320,0:12:14.240
and say has anybody defined a function
0:12:12.160,0:12:16.000
that looks like this pattern and then
0:12:14.240,0:12:17.920
and then melder says yes I did and then
0:12:16.000,0:12:19.920
we call it and then we go so it's just
0:12:17.920,0:12:21.440
it's fine it works it just adds to the
0:12:19.920,0:12:24.240
confusion why
0:12:21.440,0:12:25.440
why does it work we don't know sometimes
0:12:24.240,0:12:26.880
the only thing worse than not knowing
0:12:25.440,0:12:30.000
why something doesn't work is
0:12:26.880,0:12:30.560
not knowing why something does work um
0:12:30.000,0:12:31.920
and then
0:12:30.560,0:12:33.680
a last little bit I want to touch on
0:12:31.920,0:12:35.440
here is inheritance which is another
0:12:33.680,0:12:38.480
sort of cornerstone of object-oriented
0:12:35.440,0:12:40.160
coding as far as I can tell only uh
0:12:38.480,0:12:41.920
the only inheritance that goes on is in
0:12:40.160,0:12:45.519
something called nn male
0:12:41.920,0:12:48.399
which provides sort of common functions
0:12:45.519,0:12:49.360
for back ends that keep their mail on
0:12:48.399,0:12:52.000
your
0:12:49.360,0:12:53.680
local machine and you can spool it you
0:12:52.000,0:12:55.440
can delete it you can you know you own
0:12:53.680,0:12:56.160
the messages it's not like an nntp
0:12:55.440,0:12:59.040
server
0:12:56.160,0:13:00.160
and so a lot of those male deer nnml
0:12:59.040,0:13:02.959
whatever
0:13:00.160,0:13:04.079
a lot of those have sort of similar code
0:13:02.959,0:13:07.600
which they
0:13:04.079,0:13:09.600
which they share via this nn mail
0:13:07.600,0:13:12.959
you call it an abstract parent class I
0:13:09.600,0:13:15.440
guess so if you have something like nnml
0:13:12.959,0:13:16.720
it has a request scan uh when it goes
0:13:15.440,0:13:18.800
into request scan
0:13:16.720,0:13:21.760
it ends up calling nnmail.newmail and it
0:13:18.800,0:13:23.279
says I am calling this as an nml server
0:13:21.760,0:13:24.959
and here are some of my callback
0:13:23.279,0:13:26.000
functions and my variables that I would
0:13:24.959,0:13:28.000
like you to use
0:13:26.000,0:13:30.120
when you are getting your email so in
0:13:28.000,0:13:33.120
this way the code is sort of you know
0:13:30.120,0:13:35.680
inter-interleaved between the the child
0:13:33.120,0:13:37.120
class and the parent class even though
0:13:35.680,0:13:39.440
we're not talking in terms of classes
0:13:37.120,0:13:42.160
here at all really
0:13:39.440,0:13:42.959
so that's how noose works right now I
0:13:42.160,0:13:45.519
hope that's clear
0:13:42.959,0:13:46.560
it certainly wasn't to me and I still
0:13:45.519,0:13:48.079
have to go refresh my
0:13:46.560,0:13:50.079
memory I'd like to talk a little bit
0:13:48.079,0:13:51.600
about sort of the newer
0:13:50.079,0:13:54.240
libraries that are available now for
0:13:51.600,0:13:56.959
doing object-oriented code
0:13:54.240,0:13:59.279
uh as I mentioned I think earlier nno
0:13:56.959,0:14:00.320
the copyright headers for 1996 so that's
0:13:59.279,0:14:02.639
pretty venerable
0:14:00.320,0:14:05.519
coincidentally around the same time eric
0:14:02.639,0:14:08.320
ludlum started developing e-I-e-I-o
0:14:05.519,0:14:09.360
which is a which is sort of inspired by
0:14:08.320,0:14:12.720
a common lisp's
0:14:09.360,0:14:14.240
common lisp object system um I got a
0:14:12.720,0:14:14.959
very good introduction to that from this
0:14:14.240,0:14:16.399
book
0:14:14.959,0:14:18.000
practical common lisp which I would
0:14:16.399,0:14:20.079
encourage you to look at if you haven't
0:14:18.000,0:14:22.320
which you probably have anyway
0:14:20.079,0:14:23.920
e-I-e-I-o was incorporated into Emacs in
0:14:22.320,0:14:27.839
2010
0:14:23.920,0:14:30.240
so that yeah e-I-e-I-o provides um
0:14:27.839,0:14:32.079
the deaf class statements it provides
0:14:30.240,0:14:32.639
deaf generics deaf methods all that sort
0:14:32.079,0:14:34.800
of stuff
0:14:32.639,0:14:36.320
sort of a common lisp object-oriented
0:14:34.800,0:14:38.399
code
0:14:36.320,0:14:39.760
at some point stephan monier's money
0:14:38.399,0:14:41.199
money another name I haven't pronounced
0:14:39.760,0:14:43.839
it all out
0:14:41.199,0:14:45.120
started either cleaning up that code or
0:14:43.839,0:14:46.959
for one reason or another writing a
0:14:45.120,0:14:48.000
re-implementation of generic functions
0:14:46.959,0:14:51.440
which was added
0:14:48.000,0:14:51.920
uh in 2015 and then throughout this time
0:14:51.440,0:14:54.639
another
0:14:51.920,0:14:55.760
sort of object-oriented style
0:14:54.639,0:14:58.160
declaration is
0:14:55.760,0:15:00.000
defstruct which started off in the cl
0:14:58.160,0:15:01.600
libraries
0:15:00.000,0:15:02.959
implemented with vectors later was
0:15:01.600,0:15:04.639
implemented with records so they're
0:15:02.959,0:15:06.720
easier to target
0:15:04.639,0:15:08.399
anyway that's another option so how
0:15:06.720,0:15:09.279
would we this is I'm probably out of
0:15:08.399,0:15:13.040
time already but
0:15:09.279,0:15:13.040
we're only getting to the part
0:15:13.839,0:15:17.920
the whole point of this is how would we
0:15:15.760,0:15:19.920
rewrite someone news's code to use these
0:15:17.920,0:15:21.760
newer libraries
0:15:19.920,0:15:23.839
if we didn't have to support third party
0:15:21.760,0:15:26.639
libraries this wouldn't be that hard
0:15:23.839,0:15:28.160
but out there noose is really up on uh
0:15:26.639,0:15:30.240
you know backwards compatibility and not
0:15:28.160,0:15:33.040
breaking people's stuff and you know
0:15:30.240,0:15:34.240
multi-decade support for things so there
0:15:33.040,0:15:35.759
are people out there who have written
0:15:34.240,0:15:38.480
third-party libraries
0:15:35.759,0:15:40.000
um defining new backends for you can use
0:15:38.480,0:15:41.759
like hacker news or whatever as
0:15:40.000,0:15:43.199
a as a server so we want to be able to
0:15:41.759,0:15:44.240
support those if you didn't have to
0:15:43.199,0:15:46.079
support those it'd be fine you'd
0:15:44.240,0:15:47.440
re-implement you'd use generic functions
0:15:46.079,0:15:48.560
you'd use either structure classes
0:15:47.440,0:15:51.040
whatever but we got a
0:15:48.560,0:15:52.000
it's a little bit tricky to support
0:15:51.040,0:15:54.320
these other people's
0:15:52.000,0:15:56.079
libraries so one of the things we can do
0:15:54.320,0:15:59.279
is rewrite the defu
0:15:56.079,0:16:00.079
so if you remember defu is the thing
0:15:59.279,0:16:03.120
that uh
0:16:00.079,0:16:04.800
or sorry uh defu
0:16:03.120,0:16:07.040
is the thing that defines methods that
0:16:04.800,0:16:10.160
operate on object answers
0:16:07.040,0:16:10.639
instances and we can uh rewrite that to
0:16:10.160,0:16:13.440
use
0:16:10.639,0:16:14.240
cldef generic and that's this is fairly
0:16:13.440,0:16:15.440
fairly simple
0:16:14.240,0:16:17.759
it looks like a lot of code it's not a
0:16:15.440,0:16:20.320
lot of good for instance we have the
0:16:17.759,0:16:21.199
new closed server code that we looked at
0:16:20.320,0:16:22.720
earlier
0:16:21.199,0:16:24.560
and we have this phone call and the new
0:16:22.720,0:16:28.720
skip function so this would look
0:16:24.560,0:16:30.240
like using generic functions and methods
0:16:28.720,0:16:32.959
it would look like this we'd have
0:16:30.240,0:16:34.560
a generic def generic which is just a
0:16:32.959,0:16:36.320
sort of a declaration
0:16:34.560,0:16:37.680
and a doc string and then we have those
0:16:36.320,0:16:40.320
implementations
0:16:37.680,0:16:42.399
so we can see what the original code
0:16:40.320,0:16:44.720
does here is it first says okay what
0:16:42.399,0:16:45.839
type is our our is our argument here and
0:16:44.720,0:16:48.560
if it's a string
0:16:45.839,0:16:50.160
then go and get the proper s the proper
0:16:48.560,0:16:52.480
method definition
0:16:50.160,0:16:53.920
from that string so the way we do that
0:16:52.480,0:16:56.000
with methods is we
0:16:53.920,0:16:57.440
we say if the server is a string so if
0:16:56.000,0:16:58.720
it matches this type
0:16:57.440,0:17:00.320
then what we're going to do is just
0:16:58.720,0:17:02.160
recall we're going to call this function
0:17:00.320,0:17:05.199
all over again
0:17:02.160,0:17:06.400
using uh basically the same code here
0:17:05.199,0:17:07.600
the same code that takes a string and
0:17:06.400,0:17:10.640
gets the object so
0:17:07.600,0:17:11.600
this does this can add extra function
0:17:10.640,0:17:12.880
calls
0:17:11.600,0:17:14.880
depending on how you've written the rest
0:17:12.880,0:17:16.640
of your code um but this is sort of the
0:17:14.880,0:17:19.679
canonical way of doing this
0:17:16.640,0:17:20.559
uh using methods then our next part here
0:17:19.679,0:17:22.000
is
0:17:20.559,0:17:24.559
nishkit function we're going to get a
0:17:22.000,0:17:26.079
function called closed server
0:17:24.559,0:17:27.360
the difference here is that all these
0:17:26.079,0:17:28.000
functions are all going to be called
0:17:27.360,0:17:29.360
close
0:17:28.000,0:17:31.120
news close server they're not going to
0:17:29.360,0:17:32.799
be called news like nni my
0:17:31.120,0:17:34.400
closed server and ntp close server
0:17:32.799,0:17:36.160
they're all going to have the same name
0:17:34.400,0:17:37.440
and what we do is uh we have an around
0:17:36.160,0:17:40.640
method
0:17:37.440,0:17:43.679
for any server that is a const which is
0:17:40.640,0:17:45.520
which is as close as we care to get uh
0:17:43.679,0:17:46.799
for you know zeroing in on the type that
0:17:45.520,0:17:48.559
we're looking for
0:17:46.799,0:17:50.480
we put in a round method on that so that
0:17:48.559,0:17:51.679
we can call the next method which we'll
0:17:50.480,0:17:53.440
call the more specific
0:17:51.679,0:17:55.600
method and then we have our other
0:17:53.440,0:17:57.280
bookkeeping code to clean up you know
0:17:55.600,0:17:58.640
set up tear down code we'll go around
0:17:57.280,0:18:00.080
that
0:17:58.640,0:18:02.080
and then in one of the back-end
0:18:00.080,0:18:04.320
definitions for instance in an imap
0:18:02.080,0:18:05.760
we have another news closed server thing
0:18:04.320,0:18:08.880
this looks at the server
0:18:05.760,0:18:10.799
and it says is this server a list that
0:18:08.880,0:18:12.480
starts with a symbol and an imap and if
0:18:10.799,0:18:13.679
it is then we're almost guaranteed that
0:18:12.480,0:18:15.840
this is what we wanted
0:18:13.679,0:18:17.600
and then this is where we would insert
0:18:15.840,0:18:18.960
all the rest of the code from anonymous
0:18:17.600,0:18:20.799
closed server
0:18:18.960,0:18:22.880
where we'd re-redefine that to look like
0:18:20.799,0:18:26.080
this so it's not that hard
0:18:22.880,0:18:28.720
theoretically so what we would do
0:18:26.080,0:18:29.679
is take the defu macro macro and then
0:18:28.720,0:18:32.240
rewrite that
0:18:29.679,0:18:33.039
so that it actually defines a cl def
0:18:32.240,0:18:35.520
method like
0:18:33.039,0:18:36.320
one of these now there's a couple of
0:18:35.520,0:18:38.960
these things
0:18:36.320,0:18:41.200
unfortunately it's not that easy get rid
0:18:38.960,0:18:43.490
of you
0:18:41.200,0:18:46.400
a couple of these things
0:18:43.490,0:18:49.039
[Music]
0:18:46.400,0:18:49.919
that don't use their server as the first
0:18:49.039,0:18:52.400
argument
0:18:49.919,0:18:53.280
or any of the arguments or it's an
0:18:52.400,0:18:54.720
optional argument
0:18:53.280,0:18:56.640
and we need the server to be in there to
0:18:54.720,0:18:58.799
dispatch on its type
0:18:56.640,0:19:00.080
if the server doesn't show up as a as a
0:18:58.799,0:19:01.760
required
0:19:00.080,0:19:03.600
argument we're not going to be able to
0:19:01.760,0:19:07.440
locate the the proper
0:19:03.600,0:19:10.640
function call so in the case of
0:19:07.440,0:19:12.080
noose request group here we start with
0:19:10.640,0:19:12.720
the group it's the group that matters
0:19:12.080,0:19:14.960
and we get
0:19:12.720,0:19:16.240
the newscommand method as an optional
0:19:14.960,0:19:18.559
argument
0:19:16.240,0:19:20.480
so that's not cool we don't want that so
0:19:18.559,0:19:21.360
what we need instead is something that
0:19:20.480,0:19:23.840
looks like this
0:19:21.360,0:19:25.360
what we're going to do with uh this is
0:19:23.840,0:19:26.640
gonna be just terrible terrible code but
0:19:25.360,0:19:28.160
hopefully it won't get used very often
0:19:26.640,0:19:30.559
it's gonna be really embarrassing
0:19:28.160,0:19:31.520
um defu what's what definitely was gonna
0:19:30.559,0:19:33.200
have to do is
0:19:31.520,0:19:34.559
say okay is this a function that doesn't
0:19:33.200,0:19:35.360
have the server as the first argument
0:19:34.559,0:19:36.960
and if it does
0:19:35.360,0:19:38.400
it's gonna say oh it's news request
0:19:36.960,0:19:39.280
group what happens has to happen with
0:19:38.400,0:19:40.799
news request group
0:19:39.280,0:19:43.200
is we take the news command method and
0:19:40.799,0:19:46.240
we're going to move it up to the front
0:19:43.200,0:19:47.520
to the first argument here and it's
0:19:46.240,0:19:48.720
either going to be
0:19:47.520,0:19:50.840
it's either going to be given or it's
0:19:48.720,0:19:52.080
going to be nil because it's it is
0:19:50.840,0:19:54.320
optional
0:19:52.080,0:19:55.760
okay I briefly edited the space time
0:19:54.320,0:19:56.400
continuum there to conceal the fact that
0:19:55.760,0:19:57.679
I had
0:19:56.400,0:19:59.440
actually not finished writing the code
0:19:57.679,0:20:02.159
that I was supposed to write anyway
0:19:59.440,0:20:02.960
um so now we have once we've reordered
0:20:02.159,0:20:04.320
the
0:20:02.960,0:20:05.760
the arguments to the function then we
0:20:04.320,0:20:06.880
have to check our various possible
0:20:05.760,0:20:08.640
values one is
0:20:06.880,0:20:10.080
uh that the server was not passed in in
0:20:08.640,0:20:12.400
which case we recall
0:20:10.080,0:20:13.840
request group with the server um the
0:20:12.400,0:20:15.360
other is that it's just a string in
0:20:13.840,0:20:16.559
which case we do that and then this is
0:20:15.360,0:20:18.559
sort of the the normal
0:20:16.559,0:20:20.720
the normal case that we would expect to
0:20:18.559,0:20:21.039
cons so that's not that bad it's not you
0:20:20.720,0:20:23.760
know
0:20:21.039,0:20:24.480
it's not beautiful um I would be sort of
0:20:23.760,0:20:26.159
ashamed to
0:20:24.480,0:20:28.000
let anybody see that particular macro
0:20:26.159,0:20:30.640
but I think that it would work okay
0:20:28.000,0:20:31.440
now the more difficult thing is going to
0:20:30.640,0:20:34.640
be
0:20:31.440,0:20:37.600
the data variables so
0:20:34.640,0:20:39.360
the equivalent of def vu because our two
0:20:37.600,0:20:41.039
options for defining classes here are
0:20:39.360,0:20:41.919
def struct and def class both of which
0:20:41.039,0:20:45.280
required you
0:20:41.919,0:20:46.960
to define the slots inside this macro
0:20:45.280,0:20:49.039
itself
0:20:46.960,0:20:51.280
so defu is top level um how do we get
0:20:49.039,0:20:55.039
the top level this top level macro
0:20:51.280,0:20:56.240
uh to insert slot names into these
0:20:55.039,0:20:58.960
definitions it's
0:20:56.240,0:21:00.240
it's possible that it'll be um that I
0:20:58.960,0:21:03.039
could monkey patch
0:21:00.240,0:21:04.799
uh an existing struct or an existing
0:21:03.039,0:21:05.280
class to add a new slot into it that
0:21:04.799,0:21:07.760
sounds
0:21:05.280,0:21:09.600
ugly the other option would be to give
0:21:07.760,0:21:11.520
it a server variable slot which is just
0:21:09.600,0:21:13.760
a generalized bucket
0:21:11.520,0:21:15.520
that holds anything that gets defined
0:21:13.760,0:21:16.720
via def loop
0:21:15.520,0:21:18.799
I don't like either of those solutions
0:21:16.720,0:21:22.480
but I'm I don't see any other
0:21:18.799,0:21:25.520
any other way of doing that so we re
0:21:22.480,0:21:27.440
rewrite the nno declare macro to either
0:21:25.520,0:21:29.840
be a destructor or a def class
0:21:27.440,0:21:31.039
and we rewrite the def boom macro to
0:21:29.840,0:21:33.039
somehow
0:21:31.039,0:21:34.480
associate that variable name the symbol
0:21:33.039,0:21:36.159
with the with the resulting class
0:21:34.480,0:21:37.760
definition
0:21:36.159,0:21:39.600
then the last question is do we use
0:21:37.760,0:21:41.600
structure classes
0:21:39.600,0:21:43.200
they both got their their strengths and
0:21:41.600,0:21:46.480
their weaknesses
0:21:43.200,0:21:47.520
the nice thing is that I mean I've got
0:21:46.480,0:21:49.600
how many servers you're going to have
0:21:47.520,0:21:51.919
really I've got I think less than 10
0:21:49.600,0:21:52.960
uh truly deranged mine might have as as
0:21:51.919,0:21:55.440
many as
0:21:52.960,0:21:56.480
50 let's double that to 100 100 of
0:21:55.440,0:21:58.400
anything is not going to matter it
0:21:56.480,0:22:00.159
doesn't matter what we use
0:21:58.400,0:22:02.720
death structures are simpler they're
0:22:00.159,0:22:05.600
lighter weight they're defined on top of
0:22:02.720,0:22:06.960
the direct the c records so you know
0:22:05.600,0:22:08.559
that's nice
0:22:06.960,0:22:10.320
the slots don't carry very much
0:22:08.559,0:22:11.760
information with them there's no type
0:22:10.320,0:22:14.480
information there's no doc string for
0:22:11.760,0:22:16.559
the slots themselves
0:22:14.480,0:22:17.919
they can also only do single inheritance
0:22:16.559,0:22:21.120
which some might say
0:22:17.919,0:22:22.640
was an advantage def class each slot
0:22:21.120,0:22:24.000
gets a lot more information associated
0:22:22.640,0:22:24.480
with it with it which I think can be
0:22:24.000,0:22:27.120
nice
0:22:24.480,0:22:28.799
it can do multiple inheritance if you're
0:22:27.120,0:22:30.720
going to go there
0:22:28.799,0:22:32.640
they are heavier weight in particular
0:22:30.720,0:22:34.080
their printed representation is gross
0:22:32.640,0:22:35.840
it's enormous
0:22:34.080,0:22:37.520
so if you see one show up in a back
0:22:35.840,0:22:38.240
trace or in your messages buffer can
0:22:37.520,0:22:39.520
really
0:22:38.240,0:22:41.360
it can really blow that up and make it
0:22:39.520,0:22:43.200
hard to read this of course won't be an
0:22:41.360,0:22:46.240
issue because our code won't have any
0:22:43.200,0:22:48.320
errors in it um my argument for multiple
0:22:46.240,0:22:51.280
inheritance here is that I can imagine
0:22:48.320,0:22:52.720
new servers falling into sort of like a
0:22:51.280,0:22:56.240
little two by two matrix of
0:22:52.720,0:22:56.799
of parent classes one being news versus
0:22:56.240,0:23:00.320
mail
0:22:56.799,0:23:00.720
so news the messages belong to somebody
0:23:00.320,0:23:02.080
else
0:23:00.720,0:23:03.840
you can't touch them you can't delete
0:23:02.080,0:23:06.000
them mail meaning
0:23:03.840,0:23:08.960
the messages are under your command
0:23:06.000,0:23:11.039
either a local mail dealer a remote imap
0:23:08.960,0:23:12.640
you're allowed to spool them copy them
0:23:11.039,0:23:13.919
delete them at will
0:23:12.640,0:23:16.400
and then the other sort of line of the
0:23:13.919,0:23:19.760
matrix would be a local file system
0:23:16.400,0:23:20.559
versus some kind of a you know server
0:23:19.760,0:23:23.280
port
0:23:20.559,0:23:24.960
remote access and that second the server
0:23:23.280,0:23:26.880
port remote access thing might require
0:23:24.960,0:23:28.559
authentication it might require a keep
0:23:26.880,0:23:30.159
alive for a connection
0:23:28.559,0:23:31.600
um it's there's going to be a process
0:23:30.159,0:23:32.400
there rather than just file system
0:23:31.600,0:23:33.840
commands
0:23:32.400,0:23:35.360
so I could see if I was going to do
0:23:33.840,0:23:36.240
multiple inheritance that's what I would
0:23:35.360,0:23:39.039
do those two
0:23:36.240,0:23:40.400
those two possible parent classes anyway
0:23:39.039,0:23:41.520
that's as far as I've gotten
0:23:40.400,0:23:43.279
I thought that I would be able to write
0:23:41.520,0:23:44.720
more of this code before I did this talk
0:23:43.279,0:23:46.720
but instead I spent the whole time
0:23:44.720,0:23:48.320
messing with video codecs but that's
0:23:46.720,0:23:49.440
where we're at and I'm going to cut
0:23:48.320,0:23:50.960
myself off now
0:23:49.440,0:23:53.440
I hope there are questions I hope I'm
0:23:50.960,0:23:55.919
there to to answer your questions
0:23:53.440,0:23:57.120
and thanks very much again to everyone
0:23:55.919,0:23:59.279
involved
0:23:57.120,0:23:59.279
bye
