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

0:00:01.839,0:00:05.759
hello emacs conf

0:00:04.160,0:00:07.200
thanks very much first of all to the

0:00:05.759,0:00:09.440
organizers of the conference

0:00:07.200,0:00:10.480
and to the audience who i hope is out

0:00:09.440,0:00:12.080
there somewhere

0:00:10.480,0:00:14.240
uh for giving me this chance to talk

0:00:12.080,0:00:16.560
about emacs and some of my uh

0:00:14.240,0:00:18.480
my poking around with emacs lisp my name

0:00:16.560,0:00:20.960
is eric abrahamson i'm not

0:00:18.480,0:00:21.920
a professional programmer but i use

0:00:20.960,0:00:24.800
emacs all day

0:00:21.920,0:00:26.160
every day for writing for translating

0:00:24.800,0:00:28.160
for project management

0:00:26.160,0:00:29.199
and most importantly for email which

0:00:28.160,0:00:32.480
will be the

0:00:29.199,0:00:35.440
subject of my talk today so i'm talking

0:00:32.480,0:00:38.320
about object-oriented code in emacs

0:00:35.440,0:00:40.160
uh most famous possibly oldest

0:00:38.320,0:00:41.760
definitely most notorious news reader

0:00:40.160,0:00:44.320
slash emacs client

0:00:41.760,0:00:45.440
email client so in particular object

0:00:44.320,0:00:49.520
oriented code

0:00:45.440,0:00:49.520
in news why object-oriented code

0:00:50.239,0:00:53.600
the way news works is it started off as

0:00:51.920,0:00:57.039
a news reader so for access

0:00:53.600,0:00:59.120
accessing nntp servers and later on grew

0:00:57.039,0:01:01.039
a whole bunch of new functionality as a

0:00:59.120,0:01:02.079
mail client so it can talk to imap

0:01:01.039,0:01:04.799
servers

0:01:02.079,0:01:06.640
mail dealer directories uh folders on

0:01:04.799,0:01:08.400
your file system all kinds of stuff

0:01:06.640,0:01:09.760
but it presents a unified interface to

0:01:08.400,0:01:11.040
all those things so it's basically

0:01:09.760,0:01:14.000
polymorphism

0:01:11.040,0:01:16.400
one of the the basic fundamental

0:01:14.000,0:01:18.720
principles of object oriented code so

0:01:16.400,0:01:19.920
it's a good fit second reason is it

0:01:18.720,0:01:22.880
already is

0:01:19.920,0:01:23.759
object oriented and i'll get into what

0:01:22.880,0:01:27.280
that means

0:01:23.759,0:01:28.640
in a second so

0:01:27.280,0:01:30.640
the background that you should know is

0:01:28.640,0:01:32.560
that most of this code was written in

0:01:30.640,0:01:34.880
the 90s

0:01:32.560,0:01:36.159
emacs lisp has only grown sort of

0:01:34.880,0:01:38.640
official

0:01:36.159,0:01:41.200
object orientation support libraries

0:01:38.640,0:01:43.840
over the past 10 years or so

0:01:41.200,0:01:44.799
from about 2010 to the present so what

0:01:43.840,0:01:48.640
does

0:01:44.799,0:01:50.560
news do so the basics of

0:01:48.640,0:01:52.240
object orientation in most languages are

0:01:50.560,0:01:53.759
you you define

0:01:52.240,0:01:55.840
a class of some sort and then you

0:01:53.759,0:01:58.079
instantiate that class and these

0:01:55.840,0:02:00.320
class instances have two things they

0:01:58.079,0:02:01.759
have data attributes or

0:02:00.320,0:02:04.799
slots or members or whatever you're

0:02:01.759,0:02:07.280
going to call them and they have

0:02:04.799,0:02:08.399
methods which operate on individual

0:02:07.280,0:02:11.120
instances

0:02:08.399,0:02:12.879
so you could say that you create or

0:02:11.120,0:02:13.920
instantiate an instance of a class in

0:02:12.879,0:02:16.239
that instance

0:02:13.920,0:02:17.120
owns two things that owns its set of

0:02:16.239,0:02:20.239
attributes

0:02:17.120,0:02:23.280
and it owns some methods which

0:02:20.239,0:02:26.720
also work on the on the instance

0:02:23.280,0:02:29.040
so both in nurse's existing code and in

0:02:26.720,0:02:30.080
the more standard object oriented emacs

0:02:29.040,0:02:32.480
lisp libraries

0:02:30.080,0:02:34.080
this relationship is turned on its head

0:02:32.480,0:02:37.599
a little bit

0:02:34.080,0:02:40.239
in that data slots and

0:02:37.599,0:02:41.360
uh and instance methods are defined

0:02:40.239,0:02:42.959
outside of the

0:02:41.360,0:02:45.040
class or the instances themselves so

0:02:42.959,0:02:46.879
they are top level definitions

0:02:45.040,0:02:48.319
so we'll get to what that means in the

0:02:46.879,0:02:49.840
in the newer libraries um

0:02:48.319,0:02:51.760
in a bit but uh first i want to talk

0:02:49.840,0:02:54.319
about how news does this and in order to

0:02:51.760,0:02:57.440
do that we are going to go deep into

0:02:54.319,0:02:59.879
the darkest corner of the new co source

0:02:57.440,0:03:02.879
code tree to a library called

0:02:59.879,0:03:05.040
nno.l very cryptically

0:03:02.879,0:03:06.800
titled uh library and when we open it up

0:03:05.040,0:03:09.519
we find

0:03:06.800,0:03:11.040
a library with no code comments and

0:03:09.519,0:03:12.800
almost no doc strings

0:03:11.040,0:03:14.159
almost as if lars was a little ashamed

0:03:12.800,0:03:16.000
not ashamed but knew he was doing

0:03:14.159,0:03:19.040
something a little bit crazy

0:03:16.000,0:03:21.040
and didn't want anyone to see so

0:03:19.040,0:03:22.400
this file contains the the object

0:03:21.040,0:03:24.480
oriented mechanism

0:03:22.400,0:03:25.760
whereby you can define different kinds

0:03:24.480,0:03:27.280
of back ends for news

0:03:25.760,0:03:29.760
and then those back ends can be

0:03:27.280,0:03:32.480
instantiated as individual

0:03:29.760,0:03:33.360
servers and as you define these backends

0:03:32.480,0:03:36.000
you're supposed to use

0:03:33.360,0:03:36.640
two macros which you can see here one is

0:03:36.000,0:03:39.599
called def

0:03:36.640,0:03:41.280
vu and one is called defu and if you

0:03:39.599,0:03:43.280
look at the definitions the definitions

0:03:41.280,0:03:45.440
look pretty simple here def vu basically

0:03:43.280,0:03:49.040
turns into a def var

0:03:45.440,0:03:52.239
and foo turns into a defund

0:03:49.040,0:03:55.760
and along with those basic definitions

0:03:52.239,0:03:58.720
the library also does some registration

0:03:55.760,0:04:00.080
memoization caching of those variables

0:03:58.720,0:04:01.840
it saves them in the structure

0:04:00.080,0:04:03.360
for later use so that we know that those

0:04:01.840,0:04:05.280
are meant to be

0:04:03.360,0:04:06.640
uh attributes and methods that are used

0:04:05.280,0:04:08.000
with instances

0:04:06.640,0:04:09.280
with server instances but you can see

0:04:08.000,0:04:10.560
that there's no server instance

0:04:09.280,0:04:13.200
definition here there's no

0:04:10.560,0:04:14.239
like no nothing these are top level

0:04:13.200,0:04:18.160
these are top level

0:04:14.239,0:04:18.639
definitions so really data attributes

0:04:18.160,0:04:22.000
for

0:04:18.639,0:04:23.840
new servers and

0:04:22.000,0:04:25.440
methods or functions that operate on

0:04:23.840,0:04:28.400
those instances are completely

0:04:25.440,0:04:29.600
separate mechanisms they don't really

0:04:28.400,0:04:31.680
have anything to do with each other they

0:04:29.600,0:04:36.560
don't belong to the same data structures

0:04:31.680,0:04:36.560
so how do they work follow me

0:04:37.120,0:04:41.360
aka methods and attributes these are all

0:04:39.520,0:04:44.479
the things i just said

0:04:41.360,0:04:47.360
so when you define a

0:04:44.479,0:04:47.360
a backend type

0:04:48.560,0:04:52.400
in noose what you get is this a

0:04:51.199,0:04:54.080
definition a list

0:04:52.400,0:04:55.520
and it'll say there is such a back end

0:04:54.080,0:04:58.880
as nnml

0:04:55.520,0:04:59.520
and these are its uh data attributes

0:04:58.880,0:05:01.840
that any

0:04:59.520,0:05:02.960
given instance can have and then these

0:05:01.840,0:05:04.960
are

0:05:02.960,0:05:06.880
the functions or methods that are

0:05:04.960,0:05:08.960
defined to operate on

0:05:06.880,0:05:11.440
an instance of this backend so a server

0:05:08.960,0:05:13.360
that belongs to the nnml

0:05:11.440,0:05:15.120
backend so at least we have this data

0:05:13.360,0:05:16.880
here so that's that's handy we don't you

0:05:15.120,0:05:18.000
don't really touch that that's like very

0:05:16.880,0:05:20.560
very very deep

0:05:18.000,0:05:22.560
um use code that doesn't really come up

0:05:20.560,0:05:25.280
even as a

0:05:22.560,0:05:26.479
even as a bug squasher or whatever we

0:05:25.280,0:05:27.280
don't touch that very often but there

0:05:26.479,0:05:30.400
they are and that's

0:05:27.280,0:05:32.080
that's how they work now the next thing

0:05:30.400,0:05:34.000
that obviously you want to know is okay

0:05:32.080,0:05:35.039
where are if i've started up news where

0:05:34.000,0:05:37.199
are my servers

0:05:35.039,0:05:39.199
uh where are these server objects since

0:05:37.199,0:05:41.840
this is object oriented

0:05:39.199,0:05:43.199
programming and the weird thing that you

0:05:41.840,0:05:45.199
will eventually

0:05:43.199,0:05:46.880
figure out in some cases after years of

0:05:45.199,0:05:49.199
poking around in the new source code

0:05:46.880,0:05:50.320
is that servers do not exist in an

0:05:49.199,0:05:53.440
ontological

0:05:50.320,0:05:55.440
philosophical sense as objects the

0:05:53.440,0:05:57.039
primary data structures of noose are

0:05:55.440,0:05:58.960
groups

0:05:57.039,0:06:00.720
and in sort of an object-oriented

0:05:58.960,0:06:01.759
hierarchical you know mindset you'd

0:06:00.720,0:06:03.759
think well

0:06:01.759,0:06:05.759
groups belong to servers so servers must

0:06:03.759,0:06:08.000
exist but they don't

0:06:05.759,0:06:09.360
each group and here you can see some

0:06:08.000,0:06:11.199
examples of groups

0:06:09.360,0:06:13.039
these are basically the data structures

0:06:11.199,0:06:14.960
that represent a group each group also

0:06:13.039,0:06:17.039
has a little entry here that

0:06:14.960,0:06:18.000
that tells you what server it belongs to

0:06:17.039,0:06:20.479
and each group

0:06:18.000,0:06:23.120
replicates that data uh saying which

0:06:20.479,0:06:24.479
server it belongs to and so when

0:06:23.120,0:06:26.160
nurse is going through doing its

0:06:24.479,0:06:27.680
business uh trying to figure out what's

0:06:26.160,0:06:29.840
like updating mail from the groups or

0:06:27.680,0:06:31.600
whatever almost every time

0:06:29.840,0:06:32.960
it will cycle through all the list of

0:06:31.600,0:06:34.960
groups it'll

0:06:32.960,0:06:36.720
it'll look at all the server definitions

0:06:34.960,0:06:38.160
and it will categorize the groups by

0:06:36.720,0:06:41.120
server

0:06:38.160,0:06:42.160
which which is just weird because you're

0:06:41.120,0:06:43.840
sort of looking for okay where does the

0:06:42.160,0:06:44.479
server exist it doesn't exist it's put

0:06:43.840,0:06:48.319
together

0:06:44.479,0:06:50.400
every time uh out of out of code

0:06:48.319,0:06:51.840
elsewhere in the news code base

0:06:50.400,0:06:54.080
specifically from these group

0:06:51.840,0:06:55.199
these group definitions and so this is

0:06:54.080,0:06:58.080
very odd because

0:06:55.199,0:06:58.720
in in some sense like here this one its

0:06:58.080,0:07:02.240
server is

0:06:58.720,0:07:03.919
nnml and an empty string so there's a

0:07:02.240,0:07:04.479
certain sense here in which this server

0:07:03.919,0:07:06.400
is not

0:07:04.479,0:07:07.759
really an object at all what it is is a

0:07:06.400,0:07:08.560
set of instructions for how to find

0:07:07.759,0:07:11.199
messages

0:07:08.560,0:07:12.800
and this set of instructions is go to

0:07:11.199,0:07:15.440
the default place where the user

0:07:12.800,0:07:16.000
might have their mail and expect to find

0:07:15.440,0:07:18.080
messages

0:07:16.000,0:07:19.840
there in an nml format which is

0:07:18.080,0:07:22.479
basically just one message per

0:07:19.840,0:07:23.840
um per file and any number of groups

0:07:22.479,0:07:25.440
could have those same instructions uh

0:07:23.840,0:07:26.720
but they're not it's not really a thing

0:07:25.440,0:07:28.639
it's really just a

0:07:26.720,0:07:30.240
it's more of a procedural instruction

0:07:28.639,0:07:31.919
and on the other end of the spectrum you

0:07:30.240,0:07:33.599
might have an nni map

0:07:31.919,0:07:35.840
server which very much is a thing it has

0:07:33.599,0:07:37.759
its own it has its own server its own

0:07:35.840,0:07:40.240
port its own authentication

0:07:37.759,0:07:41.360
system so some of the servers are more

0:07:40.240,0:07:42.400
like things some of the servers are more

0:07:41.360,0:07:45.520
like instructions

0:07:42.400,0:07:47.280
as news works right now um these

0:07:45.520,0:07:48.879
most of the servers are treated like

0:07:47.280,0:07:50.879
just instruction sets

0:07:48.879,0:07:53.120
and and there's no place where you can

0:07:50.879,0:07:55.360
go and find them there's no one central

0:07:53.120,0:07:56.160
uh variable that defines them all so how

0:07:55.360,0:07:57.520
do the

0:07:56.160,0:07:59.520
um so we'll talk about the methods in a

0:07:57.520,0:08:02.639
second how do the data attributes work

0:07:59.520,0:08:04.479
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

0:08:08.080,0:08:11.120
nno

0:08:08.960,0:08:12.960
state a list and there's a concept to

0:08:11.120,0:08:16.560
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