path: root/2020/subtitles/emacsconf-2020--32-object-oriented-code-in-the-gnus-newsreader--eric-abrahamsen-autogen.sbv

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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

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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

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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

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there in an nml format which is

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basically just one message per

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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

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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

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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

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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

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your servers when they're put together

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uh they are okay they are

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kept in a variable and it's called nno

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nno

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state a list and there's a concept to

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this of the current server

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so when we go here let's go back to

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our nnno definition a list so when we

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have an nnml

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server say we have one here and it's

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just this blank string

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these are all when you define that in

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your own uh server definition code

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you can put in different values for all

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of these

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various attributes and when noose comes

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when it comes time for news to operate

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on this server in particular ask it to

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you know open a group or get new mail

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what it will do is it will take

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that particular server's data from these

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symbols

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and it will copy all that information

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into the global devfars

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so for the time that you are operating

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on this particular server

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its individual data becomes the values

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of these global

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variables which when you realize what's

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happening is sort of terrifying you

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think oh my god

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but at the same time it's actually kind

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of impressive and it's amazing that it

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works as well as it does

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I'm actually a little bit in awe of the

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of the code in this in this library I

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think it's pretty impressive

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so as you nno change server

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uh this function here these values get

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copied into the global value into the

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global variables and then as you go on

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the next server

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that gets you know cleaned out and

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recopied there are a few

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um a few other slot types

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or attribute types which do because all

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of these attributes see they all start

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with the nml

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or in this case and in folder prefix

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but there are a few slot types that all

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servers need for

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for instance their most recent status

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message a status symbol like open denied

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whatever

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and that data is sort of scattered

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around the rest of the news

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code base in various variables or

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various places

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so that's that sort of just contributes

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to the confusion when you're trying to

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figure out why

0:09:57.360,0:10:03.839
things are going wrong so that is our

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um nnoo which is and

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sort of how the attributes and these

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global variables work

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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

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and so this is the place where all the

0:10:23.200,0:10:27.200
server level methods are defined

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and what we have here are things like

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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

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it looks at the server and basically it

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finds the proper function to call on

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this particular server

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using the function new skip function by

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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