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diff --git a/2020/subtitles/emacsconf-2020--32-object-oriented-code-in-the-gnus-newsreader--eric-abrahamsen-autogen.vtt b/2020/subtitles/emacsconf-2020--32-object-oriented-code-in-the-gnus-newsreader--eric-abrahamsen-autogen.vtt new file mode 100644 index 00000000..55af2c4c --- /dev/null +++ b/2020/subtitles/emacsconf-2020--32-object-oriented-code-in-the-gnus-newsreader--eric-abrahamsen-autogen.vtt @@ -0,0 +1,2164 @@ +WEBVTT + +00:00:01.839 --> 00:00:04.160 +Hello, EmacsConf! + +00:00:04.160 --> 00:00:05.279 +Thanks very much, first of all, + +00:00:05.280 --> 00:00:07.200 +to the organizers of the conference + +00:00:07.200 --> 00:00:08.800 +and to the audience, + +00:00:08.801 --> 00:00:10.480 +who I hope is out there somewhere, + +00:00:10.480 --> 00:00:11.679 +for giving me this chance + +00:00:11.680 --> 00:00:12.880 +to talk about Emacs + +00:00:12.881 --> 00:00:16.240 +and some of my poking around with Emacs Lisp. + +00:00:16.241 --> 00:00:17.680 +My name is Eric Abrahamsen. + +00:00:17.681 --> 00:00:20.480 +I'm not a professional programmer, + +00:00:20.481 --> 00:00:23.039 +but I use Emacs all day, every day, + +00:00:23.040 --> 00:00:24.800 +for writing, for translating, + +00:00:24.800 --> 00:00:26.160 +for project management, + +00:00:26.160 --> 00:00:27.920 +and most importantly, for email, + +00:00:27.921 --> 00:00:30.640 +which will be the subject of my talk today. + +00:00:30.641 --> 00:00:32.880 +So I'm talking about + +00:00:32.881 --> 00:00:34.160 +object-oriented code + +00:00:34.161 --> 00:00:38.320 +in Emacs' most famous, possibly oldest, + +00:00:38.320 --> 00:00:39.520 +definitely most notorious + +00:00:39.521 --> 00:00:42.800 +news reader / email client, + +00:00:42.801 --> 00:00:44.000 +so, in particular, + +00:00:44.001 --> 00:00:46.000 +object-oriented code in Gnus. + +00:00:46.001 --> 00:00:50.239 +Why object-oriented code? + +00:00:50.239 --> 00:00:51.199 +The way Gnus works is + +00:00:51.200 --> 00:00:52.480 +it started off as a news reader, + +00:00:52.481 --> 00:00:55.920 +so for accessing NNTP servers + +00:00:55.921 --> 00:00:57.600 +and later on grew a whole bunch + +00:00:57.601 --> 00:00:59.760 +of new functionality as a mail client, + +00:00:59.761 --> 00:01:02.079 +so it can talk to IMAP servers, + +00:01:02.079 --> 00:01:04.320 +Maildir directories, + +00:01:04.321 --> 00:01:05.360 +folders on your file system, + +00:01:05.361 --> 00:01:06.640 +all kinds of stuff, + +00:01:06.640 --> 00:01:08.320 +but it presents a unified interface + +00:01:08.321 --> 00:01:08.960 +to all those things, + +00:01:08.961 --> 00:01:11.040 +so it's basically polymorphism, + +00:01:11.040 --> 00:01:14.560 +one of the the basic fundamental principles + +00:01:14.561 --> 00:01:15.680 +of object oriented code. + +00:01:15.681 --> 00:01:17.600 +So it's a good fit. + +00:01:17.601 --> 00:01:21.439 +Second reason is it already is object-oriented, + +00:01:21.440 --> 00:01:25.280 +and I'll get into what that means in a second. + +00:01:25.281 --> 00:01:28.479 +So the background that you should know + +00:01:28.480 --> 00:01:30.000 +is that most of this code + +00:01:30.001 --> 00:01:32.560 +was written in the 90s. + +00:01:32.560 --> 00:01:34.880 +Emacs Lisp has only grown sort of + +00:01:34.881 --> 00:01:38.640 +official object orientation support libraries + +00:01:38.640 --> 00:01:41.200 +over the past 10 years or so, + +00:01:41.200 --> 00:01:42.799 +from about 2010 to the present. + +00:01:42.800 --> 00:01:45.920 +So what does Gnus do? + +00:01:45.921 --> 00:01:49.520 +So the basics of object orientation + +00:01:49.521 --> 00:01:50.560 +in most languages are: + +00:01:50.560 --> 00:01:53.439 +you define a class of some sort, + +00:01:53.440 --> 00:01:55.040 +and then you instantiate that class. + +00:01:55.041 --> 00:01:57.920 +These class instances have two things: + +00:01:57.921 --> 00:02:00.719 +they have data attributes (or slots, + +00:02:00.720 --> 00:02:01.680 +or members, or whatever + +00:02:01.681 --> 00:02:02.640 +you're going to call them), + +00:02:02.641 --> 00:02:05.600 +and they have methods + +00:02:05.601 --> 00:02:08.399 +which operate on individual instances. + +00:02:08.399 --> 00:02:10.239 +So you could say that + +00:02:10.240 --> 00:02:11.840 +you create or instantiate + +00:02:11.841 --> 00:02:12.800 +an instance of a class, + +00:02:12.801 --> 00:02:14.800 +and that instance owns two things. + +00:02:14.801 --> 00:02:17.120 +That owns its set of attributes, + +00:02:17.120 --> 00:02:19.520 +and it owns some methods, + +00:02:19.521 --> 00:02:23.280 +which also work on the instance. + +00:02:23.280 --> 00:02:25.680 +Both in Gnus' existing code + +00:02:25.681 --> 00:02:28.560 +and in the more standard object-oriented + +00:02:28.561 --> 00:02:31.680 +Emacs Lisp libraries, this relationship + +00:02:31.681 --> 00:02:34.080 +is turned on its head a little bit, + +00:02:34.080 --> 00:02:39.599 +in that data slots and instance methods + +00:02:39.600 --> 00:02:41.760 +are defined outside of the class + +00:02:41.761 --> 00:02:42.959 +or the instances themselves. + +00:02:42.959 --> 00:02:45.040 +They are top-level definitions. + +00:02:45.040 --> 00:02:46.879 +We'll get to what that means + +00:02:46.879 --> 00:02:48.720 +in the newer libraries in a bit, + +00:02:48.721 --> 00:02:49.920 +but first I want to talk about + +00:02:49.921 --> 00:02:51.280 +how Gnus does this. + +00:02:51.281 --> 00:02:52.160 +In order to do that, + +00:02:52.161 --> 00:02:54.319 +we are going to go deep into + +00:02:54.319 --> 00:02:55.760 +the darkest corner + +00:02:55.761 --> 00:02:58.080 +of the Gnus source code tree + +00:02:58.081 --> 00:03:01.440 +to a library called nnoo.el, + +00:03:01.441 --> 00:03:04.080 +very cryptically-titled library, + +00:03:04.081 --> 00:03:06.800 +and when we open it up, we find + +00:03:06.800 --> 00:03:09.280 +a library with no code comments + +00:03:09.281 --> 00:03:11.040 +and almost no doc strings. + +00:03:11.040 --> 00:03:12.800 +Almost as if Lars was a little ashamed-- + +00:03:12.800 --> 00:03:14.159 +not ashamed, but knew he was doing + +00:03:14.159 --> 00:03:16.000 +something a little bit crazy + +00:03:16.000 --> 00:03:18.080 +and didn't want anyone to see. + +00:03:18.081 --> 00:03:20.560 +So this file contains + +00:03:20.561 --> 00:03:22.400 +the object-oriented mechanism + +00:03:22.400 --> 00:03:23.920 +whereby you can define + +00:03:23.921 --> 00:03:25.760 +different kinds of backends for Gnus, + +00:03:25.760 --> 00:03:26.799 +and then those backends + +00:03:26.800 --> 00:03:30.879 +can be instantiated as individual servers. + +00:03:30.880 --> 00:03:32.480 +As you define these backends, + +00:03:32.480 --> 00:03:34.319 +you're supposed to use two macros, + +00:03:34.320 --> 00:03:35.680 +which you can see here. + +00:03:35.681 --> 00:03:37.280 +One is called defvoo, + +00:03:37.281 --> 00:03:39.440 +and one is called deffoo. + +00:03:39.441 --> 00:03:40.400 +If you look at the definitions, + +00:03:40.401 --> 00:03:41.920 +the definitions look pretty simple. + +00:03:41.921 --> 00:03:45.440 +Here, defvoo basically turns into a defvar + +00:03:45.440 --> 00:03:49.040 +and foo turns into a defun. + +00:03:49.040 --> 00:03:52.239 +Along with those basic definitions, + +00:03:52.239 --> 00:03:55.760 +the library also does some registration, + +00:03:55.760 --> 00:03:58.720 +memoization, caching of those variables. + +00:03:58.720 --> 00:04:00.879 +It saves them in the structure for later use, + +00:04:00.880 --> 00:04:03.360 +so that we know that those are meant to be + +00:04:03.360 --> 00:04:04.799 +attributes and methods + +00:04:04.800 --> 00:04:06.640 +that are used with instances, + +00:04:06.640 --> 00:04:07.519 +with server instances. + +00:04:07.520 --> 00:04:08.159 +But you can see that + +00:04:08.160 --> 00:04:10.000 +there's no server instance definition here. + +00:04:10.001 --> 00:04:12.159 +There's no, like, no nothing. + +00:04:12.160 --> 00:04:14.799 +These are top-level definitions, + +00:04:14.800 --> 00:04:20.239 +so really, data attributes for new servers + +00:04:20.240 --> 00:04:23.040 +and methods or functions + +00:04:23.041 --> 00:04:24.639 +that operate on those instances + +00:04:24.640 --> 00:04:27.840 +are completely separate mechanisms. + +00:04:27.841 --> 00:04:29.040 +They don't really have anything to do + +00:04:29.041 --> 00:04:29.520 +with each other. + +00:04:29.521 --> 00:04:31.680 +They don't belong to the same data structures. + +00:04:31.680 --> 00:04:34.080 +So how do they work? + +00:04:34.081 --> 00:04:37.120 +Follow me. deffoo and defvoo, + +00:04:37.120 --> 00:04:38.960 +aka methods and attributes, + +00:04:38.961 --> 00:04:41.360 +these are all the things I just said. + +00:04:41.360 --> 00:04:50.240 +So when you define a a backend type in Gnus, + +00:04:50.241 --> 00:04:52.400 +what you get is this: a definition, a list. + +00:04:52.400 --> 00:04:55.520 +It'll say, there is such a backend as nnml, + +00:04:55.520 --> 00:04:58.880 +and these are its data attributes + +00:04:58.880 --> 00:05:01.039 +that any given instance can have, + +00:05:01.040 --> 00:05:04.720 +and then these are the functions or methods + +00:05:04.721 --> 00:05:06.880 +that are defined to operate on + +00:05:06.880 --> 00:05:08.240 +an instance of this backend, + +00:05:08.241 --> 00:05:09.600 +so a server that belongs to + +00:05:09.601 --> 00:05:12.160 +the nnml backend. + +00:05:12.161 --> 00:05:13.600 +So at least we have this data here. + +00:05:13.601 --> 00:05:16.080 +That's handy. We don't really touch that. + +00:05:16.081 --> 00:05:19.600 +That's, like, very, very, very deep Gnus code + +00:05:19.601 --> 00:05:20.560 +that doesn't really come up + +00:05:20.560 --> 00:05:25.199 +even as a bug squasher or whatever. + +00:05:25.200 --> 00:05:26.160 +We don't touch that very often, + +00:05:26.161 --> 00:05:26.800 +but there they are, + +00:05:26.801 --> 00:05:29.199 +and that's how they work. + +00:05:29.200 --> 00:05:31.039 +Now the next thing that obviously + +00:05:31.040 --> 00:05:32.080 +you want to know is, okay, + +00:05:32.080 --> 00:05:33.759 +where are... if I've started up Gnus, + +00:05:33.760 --> 00:05:35.039 +where are my servers? + +00:05:35.039 --> 00:05:36.880 +Where are these server objects, + +00:05:36.881 --> 00:05:40.479 +since this is object-oriented programming? + +00:05:40.480 --> 00:05:41.520 +And the weird thing + +00:05:41.521 --> 00:05:43.759 +that you will eventually figure out + +00:05:43.760 --> 00:05:45.680 +(in some cases, after years of poking around) + +00:05:45.681 --> 00:05:46.880 +in the Gnus source code + +00:05:46.880 --> 00:05:48.880 +is that servers do not exist + +00:05:48.881 --> 00:05:51.360 +in an ontological, philosophical sense, + +00:05:51.361 --> 00:05:55.280 +as objects. The primary data structures of Gnus + +00:05:55.281 --> 00:05:58.160 +are groups, and in sort of + +00:05:58.161 --> 00:06:00.560 +an object-oriented hierarchical mindset, + +00:06:00.561 --> 00:06:03.039 +you'd think, well, groups belong to servers, + +00:06:03.040 --> 00:06:05.759 +so servers must exist, but they don't. + +00:06:05.759 --> 00:06:07.840 +Each group... And here you can see + +00:06:07.841 --> 00:06:09.360 +some examples of groups... + +00:06:09.360 --> 00:06:11.199 +These are basically the data structures + +00:06:11.199 --> 00:06:12.240 +that represent a group. + +00:06:12.241 --> 00:06:14.160 +Each group also has a little entry here + +00:06:14.161 --> 00:06:17.039 +that tells you what server it belongs to, + +00:06:17.039 --> 00:06:20.080 +and each group replicates that data, + +00:06:20.081 --> 00:06:21.600 +saying which server it belongs to. + +00:06:21.601 --> 00:06:24.000 +So when Gnus is going through + +00:06:24.001 --> 00:06:25.280 +doing its business, + +00:06:25.281 --> 00:06:27.039 +trying to figure out updating mail + +00:06:27.040 --> 00:06:28.479 +from the groups or whatever, + +00:06:28.480 --> 00:06:30.960 +almost every time, it will cycle through + +00:06:30.961 --> 00:06:32.960 +all the list of groups. + +00:06:32.960 --> 00:06:34.960 +It'll look at all the server definitions, + +00:06:34.960 --> 00:06:38.160 +and it will categorize the groups by server, + +00:06:38.160 --> 00:06:40.000 +which is just weird, + +00:06:40.001 --> 00:06:41.680 +because you're sort of looking for... + +00:06:41.681 --> 00:06:42.720 +okay, where does the server exist? + +00:06:42.721 --> 00:06:43.440 +It doesn't exist. + +00:06:43.441 --> 00:06:46.240 +It's put together every time + +00:06:46.241 --> 00:06:50.400 +out of code elsewhere in the Gnus code base, + +00:06:50.400 --> 00:06:53.599 +specifically from these group definitions. + +00:06:53.600 --> 00:06:54.479 +So this is very odd, + +00:06:54.480 --> 00:06:56.319 +because in some sense... + +00:06:56.320 --> 00:06:59.360 +Like here, this one, its server is nnml + +00:06:59.361 --> 00:07:01.680 +and an empty string, + +00:07:01.681 --> 00:07:02.880 +so there's a certain sense here + +00:07:02.881 --> 00:07:04.720 +in which this server is not really + +00:07:04.721 --> 00:07:06.160 +an object at all. What it is + +00:07:06.161 --> 00:07:07.120 +is a set of instructions + +00:07:07.121 --> 00:07:08.560 +for how to find messages, + +00:07:08.560 --> 00:07:10.319 +and this set of instructions is: + +00:07:10.320 --> 00:07:12.000 +go to the default place + +00:07:12.001 --> 00:07:14.000 +where the user might have their mail + +00:07:14.001 --> 00:07:16.319 +and expect to find messages there + +00:07:16.320 --> 00:07:18.479 +in an nnml format, which is basically + +00:07:18.480 --> 00:07:21.759 +just one message per file. + +00:07:21.760 --> 00:07:22.720 +Any number of groups could have + +00:07:22.721 --> 00:07:24.400 +those same instructions, but they're not... + +00:07:24.401 --> 00:07:25.440 +It's not really a thing. + +00:07:25.440 --> 00:07:26.720 +It's really just a... + +00:07:26.720 --> 00:07:28.639 +It's more of a procedural instruction. + +00:07:28.639 --> 00:07:30.160 +On the other end of the spectrum, + +00:07:30.161 --> 00:07:32.240 +you might have an nnimap server, + +00:07:32.241 --> 00:07:33.280 +which very much is a thing. + +00:07:33.281 --> 00:07:36.160 +It has its own server, its own port, + +00:07:36.161 --> 00:07:38.960 +its own authentication system. + +00:07:38.961 --> 00:07:40.639 +So some of the servers are more like things, + +00:07:40.640 --> 00:07:42.400 +some of the servers are more like instructions. + +00:07:42.400 --> 00:07:45.520 +As Gnus works right now, + +00:07:45.520 --> 00:07:47.280 +most of the servers are treated like + +00:07:47.280 --> 00:07:48.879 +just instruction sets, + +00:07:48.879 --> 00:07:50.879 +and there's no place where you can + +00:07:50.880 --> 00:07:51.840 +go and find them. + +00:07:51.841 --> 00:07:53.680 +There's no one central variable + +00:07:53.681 --> 00:07:56.160 +that defines them all. So how do the... + +00:07:56.160 --> 00:07:57.759 +We'll talk about the methods in a second. + +00:07:57.760 --> 00:07:59.520 +How do the data attributes work? + +00:07:59.520 --> 00:08:02.639 +Put very crudely, + +00:08:02.639 --> 00:08:04.479 +your servers, when they're put together, + +00:08:04.479 --> 00:08:06.879 +they are kept in a variable, + +00:08:06.880 --> 00:08:08.080 +and it's called nnoo + +00:08:08.080 --> 00:08:08.960 +nno + +00:08:08.960 --> 00:08:11.120 +state a list and there's a concept to + +00:08:11.120 --> 00:08:12.960 +this of the current server + +00:08:12.960 --> 00:08:16.560 +so when we go here let's go back to + +00:08:16.560 --> 00:08:19.039 +our nnno definition a list so when we + +00:08:19.039 --> 00:08:20.560 +have an nnml + +00:08:20.560 --> 00:08:22.240 +server say we have one here and it's + +00:08:22.240 --> 00:08:24.400 +just this blank string + +00:08:24.400 --> 00:08:26.639 +these are all when you define that in + +00:08:26.639 --> 00:08:28.879 +your own uh server definition code + +00:08:28.879 --> 00:08:31.919 +you can put in different values for all + +00:08:31.919 --> 00:08:32.399 +of these + +00:08:32.399 --> 00:08:35.760 +various attributes and when noose comes + +00:08:35.760 --> 00:08:37.039 +when it comes time for news to operate + +00:08:37.039 --> 00:08:38.959 +on this server in particular ask it to + +00:08:38.959 --> 00:08:40.640 +you know open a group or get new mail + +00:08:40.640 --> 00:08:42.080 +what it will do is it will take + +00:08:42.080 --> 00:08:45.360 +that particular server's data from these + +00:08:45.360 --> 00:08:45.920 +symbols + +00:08:45.920 --> 00:08:47.600 +and it will copy all that information + +00:08:47.600 --> 00:08:49.600 +into the global devfars + +00:08:49.600 --> 00:08:51.760 +so for the time that you are operating + +00:08:51.760 --> 00:08:53.120 +on this particular server + +00:08:53.120 --> 00:08:55.920 +its individual data becomes the values + +00:08:55.920 --> 00:08:56.800 +of these global + +00:08:56.800 --> 00:08:59.360 +variables which when you realize what's + +00:08:59.360 --> 00:09:00.560 +happening is sort of terrifying you + +00:09:00.560 --> 00:09:02.080 +think oh my god + +00:09:02.080 --> 00:09:04.480 +but at the same time it's actually kind + +00:09:04.480 --> 00:09:05.760 +of impressive and it's amazing that it + +00:09:05.760 --> 00:09:07.279 +works as well as it does + +00:09:07.279 --> 00:09:09.120 +I'm actually a little bit in awe of the + +00:09:09.120 --> 00:09:10.880 +of the code in this in this library I + +00:09:10.880 --> 00:09:12.560 +think it's pretty impressive + +00:09:12.560 --> 00:09:15.760 +so as you nno change server + +00:09:15.760 --> 00:09:18.320 +uh this function here these values get + +00:09:18.320 --> 00:09:20.080 +copied into the global value into the + +00:09:20.080 --> 00:09:21.440 +global variables and then as you go on + +00:09:21.440 --> 00:09:22.399 +the next server + +00:09:22.399 --> 00:09:24.000 +that gets you know cleaned out and + +00:09:24.000 --> 00:09:26.399 +recopied there are a few + +00:09:26.399 --> 00:09:29.680 +um a few other slot types + +00:09:29.680 --> 00:09:32.000 +or attribute types which do because all + +00:09:32.000 --> 00:09:33.440 +of these attributes see they all start + +00:09:33.440 --> 00:09:34.720 +with the nml + +00:09:34.720 --> 00:09:37.920 +or in this case and in folder prefix + +00:09:37.920 --> 00:09:40.560 +but there are a few slot types that all + +00:09:40.560 --> 00:09:41.760 +servers need for + +00:09:41.760 --> 00:09:43.279 +for instance their most recent status + +00:09:43.279 --> 00:09:45.920 +message a status symbol like open denied + +00:09:45.920 --> 00:09:46.640 +whatever + +00:09:46.640 --> 00:09:48.080 +and that data is sort of scattered + +00:09:48.080 --> 00:09:49.680 +around the rest of the news + +00:09:49.680 --> 00:09:51.200 +code base in various variables or + +00:09:51.200 --> 00:09:53.440 +various places + +00:09:53.440 --> 00:09:55.440 +so that's that sort of just contributes + +00:09:55.440 --> 00:09:56.560 +to the confusion when you're trying to + +00:09:56.560 --> 00:09:57.360 +figure out why + +00:09:57.360 --> 00:10:00.720 +things are going wrong so that is our + +00:10:00.720 --> 00:10:03.839 +um nnoo which is and + +00:10:03.839 --> 00:10:05.440 +sort of how the attributes and these + +00:10:05.440 --> 00:10:07.360 +global variables work + +00:10:07.360 --> 00:10:09.120 +if we want to talk about defu and the + +00:10:09.120 --> 00:10:10.480 +methods we + +00:10:10.480 --> 00:10:20.800 +go to + +00:10:20.800 --> 00:10:23.200 +and so this is the place where all the + +00:10:23.200 --> 00:10:25.600 +server level methods are defined + +00:10:25.600 --> 00:10:27.200 +and what we have here are things like + +00:10:27.200 --> 00:10:29.279 +here's an example there's closed server + +00:10:29.279 --> 00:10:32.640 +this closed server is given a + +00:10:32.640 --> 00:10:36.320 +a server as a an argument + +00:10:36.320 --> 00:10:38.079 +it looks at the server and basically it + +00:10:38.079 --> 00:10:40.560 +finds the proper function to call on + +00:10:40.560 --> 00:10:42.079 +this particular server + +00:10:42.079 --> 00:10:45.120 +using the function new skip function by + +00:10:45.120 --> 00:10:45.600 +taking + +00:10:45.600 --> 00:10:48.959 +the sort of latter half of this function + +00:10:48.959 --> 00:10:49.760 +symbol + +00:10:49.760 --> 00:10:52.079 +and pasting it together with the symbol + +00:10:52.079 --> 00:10:53.440 +that represents the back end so + +00:10:53.440 --> 00:10:56.800 +if you were calling this on an nni map + +00:10:56.800 --> 00:10:59.600 +server your skip function would look at + +00:10:59.600 --> 00:11:01.279 +your imap server look at closed server I + +00:11:01.279 --> 00:11:02.240 +knew what + +00:11:02.240 --> 00:11:07.839 +it would come up with + +00:11:07.839 --> 00:11:10.240 +server sure enough there's an imac close + +00:11:10.240 --> 00:11:11.920 +server and it'll call this code and then + +00:11:11.920 --> 00:11:12.240 +it'll + +00:11:12.240 --> 00:11:14.000 +it'll go and do its other bookkeeping + +00:11:14.000 --> 00:11:15.279 +another sort of + +00:11:15.279 --> 00:11:18.320 +surrounding code and so that's not that + +00:11:18.320 --> 00:11:19.279 +actually works pretty well + +00:11:19.279 --> 00:11:22.640 +uh as as things go uh defu + +00:11:22.640 --> 00:11:24.959 +makes a record that this this function + +00:11:24.959 --> 00:11:26.800 +exists and nus gets function get + +00:11:26.800 --> 00:11:28.320 +function looks on that cache finds the + +00:11:28.320 --> 00:11:29.600 +function and calls it + +00:11:29.600 --> 00:11:30.959 +now what's particularly confusing is + +00:11:30.959 --> 00:11:32.560 +that you don't actually even have to use + +00:11:32.560 --> 00:11:33.360 +defu + +00:11:33.360 --> 00:11:35.519 +so whoever wrote and then mail gear + +00:11:35.519 --> 00:11:38.399 +which is a weird library + +00:11:38.399 --> 00:11:39.920 +said to heck with you I'm not using any + +00:11:39.920 --> 00:11:41.600 +of these + +00:11:41.600 --> 00:11:43.120 +any of this machinery I'm going to do it + +00:11:43.120 --> 00:11:45.839 +myself so we have + +00:11:45.839 --> 00:11:49.680 +def structs to hold uh the instance + +00:11:49.680 --> 00:11:52.320 +data and then we have just plain old + +00:11:52.320 --> 00:11:53.040 +defense + +00:11:53.040 --> 00:11:55.680 +for things like animal your close server + +00:11:55.680 --> 00:11:57.279 +request close all of these + +00:11:57.279 --> 00:11:59.279 +these server level uh variables and it + +00:11:59.279 --> 00:12:00.320 +just turns out that + +00:12:00.320 --> 00:12:03.360 +news in its belt and suspenders + +00:12:03.360 --> 00:12:05.839 +approach to uh to coding it'll actually + +00:12:05.839 --> 00:12:07.279 +just go out if it can't find + +00:12:07.279 --> 00:12:10.320 +the memoized function it'll just go out + +00:12:10.320 --> 00:12:12.160 +and say has anybody defined a function + +00:12:12.160 --> 00:12:14.240 +that looks like this pattern and then + +00:12:14.240 --> 00:12:16.000 +and then melder says yes I did and then + +00:12:16.000 --> 00:12:17.920 +we call it and then we go so it's just + +00:12:17.920 --> 00:12:19.920 +it's fine it works it just adds to the + +00:12:19.920 --> 00:12:21.440 +confusion why + +00:12:21.440 --> 00:12:24.240 +why does it work we don't know sometimes + +00:12:24.240 --> 00:12:25.440 +the only thing worse than not knowing + +00:12:25.440 --> 00:12:26.880 +why something doesn't work is + +00:12:26.880 --> 00:12:30.000 +not knowing why something does work um + +00:12:30.000 --> 00:12:30.560 +and then + +00:12:30.560 --> 00:12:31.920 +a last little bit I want to touch on + +00:12:31.920 --> 00:12:33.680 +here is inheritance which is another + +00:12:33.680 --> 00:12:35.440 +sort of cornerstone of object-oriented + +00:12:35.440 --> 00:12:38.480 +coding as far as I can tell only uh + +00:12:38.480 --> 00:12:40.160 +the only inheritance that goes on is in + +00:12:40.160 --> 00:12:41.920 +something called nn male + +00:12:41.920 --> 00:12:45.519 +which provides sort of common functions + +00:12:45.519 --> 00:12:48.399 +for back ends that keep their mail on + +00:12:48.399 --> 00:12:49.360 +your + +00:12:49.360 --> 00:12:52.000 +local machine and you can spool it you + +00:12:52.000 --> 00:12:53.680 +can delete it you can you know you own + +00:12:53.680 --> 00:12:55.440 +the messages it's not like an nntp + +00:12:55.440 --> 00:12:56.160 +server + +00:12:56.160 --> 00:12:59.040 +and so a lot of those male deer nnml + +00:12:59.040 --> 00:13:00.160 +whatever + +00:13:00.160 --> 00:13:02.959 +a lot of those have sort of similar code + +00:13:02.959 --> 00:13:04.079 +which they + +00:13:04.079 --> 00:13:07.600 +which they share via this nn mail + +00:13:07.600 --> 00:13:09.600 +you call it an abstract parent class I + +00:13:09.600 --> 00:13:12.959 +guess so if you have something like nnml + +00:13:12.959 --> 00:13:15.440 +it has a request scan uh when it goes + +00:13:15.440 --> 00:13:16.720 +into request scan + +00:13:16.720 --> 00:13:18.800 +it ends up calling nnmail.newmail and it + +00:13:18.800 --> 00:13:21.760 +says I am calling this as an nml server + +00:13:21.760 --> 00:13:23.279 +and here are some of my callback + +00:13:23.279 --> 00:13:24.959 +functions and my variables that I would + +00:13:24.959 --> 00:13:26.000 +like you to use + +00:13:26.000 --> 00:13:28.000 +when you are getting your email so in + +00:13:28.000 --> 00:13:30.120 +this way the code is sort of you know + +00:13:30.120 --> 00:13:33.120 +inter-interleaved between the the child + +00:13:33.120 --> 00:13:35.680 +class and the parent class even though + +00:13:35.680 --> 00:13:37.120 +we're not talking in terms of classes + +00:13:37.120 --> 00:13:39.440 +here at all really + +00:13:39.440 --> 00:13:42.160 +so that's how noose works right now I + +00:13:42.160 --> 00:13:42.959 +hope that's clear + +00:13:42.959 --> 00:13:45.519 +it certainly wasn't to me and I still + +00:13:45.519 --> 00:13:46.560 +have to go refresh my + +00:13:46.560 --> 00:13:48.079 +memory I'd like to talk a little bit + +00:13:48.079 --> 00:13:50.079 +about sort of the newer + +00:13:50.079 --> 00:13:51.600 +libraries that are available now for + +00:13:51.600 --> 00:13:54.240 +doing object-oriented code + +00:13:54.240 --> 00:13:56.959 +uh as I mentioned I think earlier nno + +00:13:56.959 --> 00:13:59.279 +the copyright headers for 1996 so that's + +00:13:59.279 --> 00:14:00.320 +pretty venerable + +00:14:00.320 --> 00:14:02.639 +coincidentally around the same time eric + +00:14:02.639 --> 00:14:05.519 +ludlum started developing e-I-e-I-o + +00:14:05.519 --> 00:14:08.320 +which is a which is sort of inspired by + +00:14:08.320 --> 00:14:09.360 +a common lisp's + +00:14:09.360 --> 00:14:12.720 +common lisp object system um I got a + +00:14:12.720 --> 00:14:14.240 +very good introduction to that from this + +00:14:14.240 --> 00:14:14.959 +book + +00:14:14.959 --> 00:14:16.399 +practical common lisp which I would + +00:14:16.399 --> 00:14:18.000 +encourage you to look at if you haven't + +00:14:18.000 --> 00:14:20.079 +which you probably have anyway + +00:14:20.079 --> 00:14:22.320 +e-I-e-I-o was incorporated into Emacs in + +00:14:22.320 --> 00:14:23.920 +2010 + +00:14:23.920 --> 00:14:27.839 +so that yeah e-I-e-I-o provides um + +00:14:27.839 --> 00:14:30.240 +the deaf class statements it provides + +00:14:30.240 --> 00:14:32.079 +deaf generics deaf methods all that sort + +00:14:32.079 --> 00:14:32.639 +of stuff + +00:14:32.639 --> 00:14:34.800 +sort of a common lisp object-oriented + +00:14:34.800 --> 00:14:36.320 +code + +00:14:36.320 --> 00:14:38.399 +at some point stephan monier's money + +00:14:38.399 --> 00:14:39.760 +money another name I haven't pronounced + +00:14:39.760 --> 00:14:41.199 +it all out + +00:14:41.199 --> 00:14:43.839 +started either cleaning up that code or + +00:14:43.839 --> 00:14:45.120 +for one reason or another writing a + +00:14:45.120 --> 00:14:46.959 +re-implementation of generic functions + +00:14:46.959 --> 00:14:48.000 +which was added + +00:14:48.000 --> 00:14:51.440 +uh in 2015 and then throughout this time + +00:14:51.440 --> 00:14:51.920 +another + +00:14:51.920 --> 00:14:54.639 +sort of object-oriented style + +00:14:54.639 --> 00:14:55.760 +declaration is + +00:14:55.760 --> 00:14:58.160 +defstruct which started off in the cl + +00:14:58.160 --> 00:15:00.000 +libraries + +00:15:00.000 --> 00:15:01.600 +implemented with vectors later was + +00:15:01.600 --> 00:15:02.959 +implemented with records so they're + +00:15:02.959 --> 00:15:04.639 +easier to target + +00:15:04.639 --> 00:15:06.720 +anyway that's another option so how + +00:15:06.720 --> 00:15:08.399 +would we this is I'm probably out of + +00:15:08.399 --> 00:15:09.279 +time already but + +00:15:09.279 --> 00:15:13.839 +we're only getting to the part + +00:15:13.839 --> 00:15:15.760 +the whole point of this is how would we + +00:15:15.760 --> 00:15:17.920 +rewrite someone news's code to use these + +00:15:17.920 --> 00:15:19.920 +newer libraries + +00:15:19.920 --> 00:15:21.760 +if we didn't have to support third party + +00:15:21.760 --> 00:15:23.839 +libraries this wouldn't be that hard + +00:15:23.839 --> 00:15:26.639 +but out there noose is really up on uh + +00:15:26.639 --> 00:15:28.160 +you know backwards compatibility and not + +00:15:28.160 --> 00:15:30.240 +breaking people's stuff and you know + +00:15:30.240 --> 00:15:33.040 +multi-decade support for things so there + +00:15:33.040 --> 00:15:34.240 +are people out there who have written + +00:15:34.240 --> 00:15:35.759 +third-party libraries + +00:15:35.759 --> 00:15:38.480 +um defining new backends for you can use + +00:15:38.480 --> 00:15:40.000 +like hacker news or whatever as + +00:15:40.000 --> 00:15:41.759 +a as a server so we want to be able to + +00:15:41.759 --> 00:15:43.199 +support those if you didn't have to + +00:15:43.199 --> 00:15:44.240 +support those it'd be fine you'd + +00:15:44.240 --> 00:15:46.079 +re-implement you'd use generic functions + +00:15:46.079 --> 00:15:47.440 +you'd use either structure classes + +00:15:47.440 --> 00:15:48.560 +whatever but we got a + +00:15:48.560 --> 00:15:51.040 +it's a little bit tricky to support + +00:15:51.040 --> 00:15:52.000 +these other people's + +00:15:52.000 --> 00:15:54.320 +libraries so one of the things we can do + +00:15:54.320 --> 00:15:56.079 +is rewrite the defu + +00:15:56.079 --> 00:15:59.279 +so if you remember defu is the thing + +00:15:59.279 --> 00:16:00.079 +that uh + +00:16:00.079 --> 00:16:03.120 +or sorry uh defu + +00:16:03.120 --> 00:16:04.800 +is the thing that defines methods that + +00:16:04.800 --> 00:16:07.040 +operate on object answers + +00:16:07.040 --> 00:16:10.160 +instances and we can uh rewrite that to + +00:16:10.160 --> 00:16:10.639 +use + +00:16:10.639 --> 00:16:13.440 +cldef generic and that's this is fairly + +00:16:13.440 --> 00:16:14.240 +fairly simple + +00:16:14.240 --> 00:16:15.440 +it looks like a lot of code it's not a + +00:16:15.440 --> 00:16:17.759 +lot of good for instance we have the + +00:16:17.759 --> 00:16:20.320 +new closed server code that we looked at + +00:16:20.320 --> 00:16:21.199 +earlier + +00:16:21.199 --> 00:16:22.720 +and we have this phone call and the new + +00:16:22.720 --> 00:16:24.560 +skip function so this would look + +00:16:24.560 --> 00:16:28.720 +like using generic functions and methods + +00:16:28.720 --> 00:16:30.240 +it would look like this we'd have + +00:16:30.240 --> 00:16:32.959 +a generic def generic which is just a + +00:16:32.959 --> 00:16:34.560 +sort of a declaration + +00:16:34.560 --> 00:16:36.320 +and a doc string and then we have those + +00:16:36.320 --> 00:16:37.680 +implementations + +00:16:37.680 --> 00:16:40.320 +so we can see what the original code + +00:16:40.320 --> 00:16:42.399 +does here is it first says okay what + +00:16:42.399 --> 00:16:44.720 +type is our our is our argument here and + +00:16:44.720 --> 00:16:45.839 +if it's a string + +00:16:45.839 --> 00:16:48.560 +then go and get the proper s the proper + +00:16:48.560 --> 00:16:50.160 +method definition + +00:16:50.160 --> 00:16:52.480 +from that string so the way we do that + +00:16:52.480 --> 00:16:53.920 +with methods is we + +00:16:53.920 --> 00:16:56.000 +we say if the server is a string so if + +00:16:56.000 --> 00:16:57.440 +it matches this type + +00:16:57.440 --> 00:16:58.720 +then what we're going to do is just + +00:16:58.720 --> 00:17:00.320 +recall we're going to call this function + +00:17:00.320 --> 00:17:02.160 +all over again + +00:17:02.160 --> 00:17:05.199 +using uh basically the same code here + +00:17:05.199 --> 00:17:06.400 +the same code that takes a string and + +00:17:06.400 --> 00:17:07.600 +gets the object so + +00:17:07.600 --> 00:17:10.640 +this does this can add extra function + +00:17:10.640 --> 00:17:11.600 +calls + +00:17:11.600 --> 00:17:12.880 +depending on how you've written the rest + +00:17:12.880 --> 00:17:14.880 +of your code um but this is sort of the + +00:17:14.880 --> 00:17:16.640 +canonical way of doing this + +00:17:16.640 --> 00:17:19.679 +uh using methods then our next part here + +00:17:19.679 --> 00:17:20.559 +is + +00:17:20.559 --> 00:17:22.000 +nishkit function we're going to get a + +00:17:22.000 --> 00:17:24.559 +function called closed server + +00:17:24.559 --> 00:17:26.079 +the difference here is that all these + +00:17:26.079 --> 00:17:27.360 +functions are all going to be called + +00:17:27.360 --> 00:17:28.000 +close + +00:17:28.000 --> 00:17:29.360 +news close server they're not going to + +00:17:29.360 --> 00:17:31.120 +be called news like nni my + +00:17:31.120 --> 00:17:32.799 +closed server and ntp close server + +00:17:32.799 --> 00:17:34.400 +they're all going to have the same name + +00:17:34.400 --> 00:17:36.160 +and what we do is uh we have an around + +00:17:36.160 --> 00:17:37.440 +method + +00:17:37.440 --> 00:17:40.640 +for any server that is a const which is + +00:17:40.640 --> 00:17:43.679 +which is as close as we care to get uh + +00:17:43.679 --> 00:17:45.520 +for you know zeroing in on the type that + +00:17:45.520 --> 00:17:46.799 +we're looking for + +00:17:46.799 --> 00:17:48.559 +we put in a round method on that so that + +00:17:48.559 --> 00:17:50.480 +we can call the next method which we'll + +00:17:50.480 --> 00:17:51.679 +call the more specific + +00:17:51.679 --> 00:17:53.440 +method and then we have our other + +00:17:53.440 --> 00:17:55.600 +bookkeeping code to clean up you know + +00:17:55.600 --> 00:17:57.280 +set up tear down code we'll go around + +00:17:57.280 --> 00:17:58.640 +that + +00:17:58.640 --> 00:18:00.080 +and then in one of the back-end + +00:18:00.080 --> 00:18:02.080 +definitions for instance in an imap + +00:18:02.080 --> 00:18:04.320 +we have another news closed server thing + +00:18:04.320 --> 00:18:05.760 +this looks at the server + +00:18:05.760 --> 00:18:08.880 +and it says is this server a list that + +00:18:08.880 --> 00:18:10.799 +starts with a symbol and an imap and if + +00:18:10.799 --> 00:18:12.480 +it is then we're almost guaranteed that + +00:18:12.480 --> 00:18:13.679 +this is what we wanted + +00:18:13.679 --> 00:18:15.840 +and then this is where we would insert + +00:18:15.840 --> 00:18:17.600 +all the rest of the code from anonymous + +00:18:17.600 --> 00:18:18.960 +closed server + +00:18:18.960 --> 00:18:20.799 +where we'd re-redefine that to look like + +00:18:20.799 --> 00:18:22.880 +this so it's not that hard + +00:18:22.880 --> 00:18:26.080 +theoretically so what we would do + +00:18:26.080 --> 00:18:28.720 +is take the defu macro macro and then + +00:18:28.720 --> 00:18:29.679 +rewrite that + +00:18:29.679 --> 00:18:32.240 +so that it actually defines a cl def + +00:18:32.240 --> 00:18:33.039 +method like + +00:18:33.039 --> 00:18:35.520 +one of these now there's a couple of + +00:18:35.520 --> 00:18:36.320 +these things + +00:18:36.320 --> 00:18:38.960 +unfortunately it's not that easy get rid + +00:18:38.960 --> 00:18:41.200 +of you + +00:18:41.200 --> 00:18:43.490 +a couple of these things + +00:18:43.490 --> 00:18:46.400 +[Music] + +00:18:46.400 --> 00:18:49.039 +that don't use their server as the first + +00:18:49.039 --> 00:18:49.919 +argument + +00:18:49.919 --> 00:18:52.400 +or any of the arguments or it's an + +00:18:52.400 --> 00:18:53.280 +optional argument + +00:18:53.280 --> 00:18:54.720 +and we need the server to be in there to + +00:18:54.720 --> 00:18:56.640 +dispatch on its type + +00:18:56.640 --> 00:18:58.799 +if the server doesn't show up as a as a + +00:18:58.799 --> 00:19:00.080 +required + +00:19:00.080 --> 00:19:01.760 +argument we're not going to be able to + +00:19:01.760 --> 00:19:03.600 +locate the the proper + +00:19:03.600 --> 00:19:07.440 +function call so in the case of + +00:19:07.440 --> 00:19:10.640 +noose request group here we start with + +00:19:10.640 --> 00:19:12.080 +the group it's the group that matters + +00:19:12.080 --> 00:19:12.720 +and we get + +00:19:12.720 --> 00:19:14.960 +the newscommand method as an optional + +00:19:14.960 --> 00:19:16.240 +argument + +00:19:16.240 --> 00:19:18.559 +so that's not cool we don't want that so + +00:19:18.559 --> 00:19:20.480 +what we need instead is something that + +00:19:20.480 --> 00:19:21.360 +looks like this + +00:19:21.360 --> 00:19:23.840 +what we're going to do with uh this is + +00:19:23.840 --> 00:19:25.360 +gonna be just terrible terrible code but + +00:19:25.360 --> 00:19:26.640 +hopefully it won't get used very often + +00:19:26.640 --> 00:19:28.160 +it's gonna be really embarrassing + +00:19:28.160 --> 00:19:30.559 +um defu what's what definitely was gonna + +00:19:30.559 --> 00:19:31.520 +have to do is + +00:19:31.520 --> 00:19:33.200 +say okay is this a function that doesn't + +00:19:33.200 --> 00:19:34.559 +have the server as the first argument + +00:19:34.559 --> 00:19:35.360 +and if it does + +00:19:35.360 --> 00:19:36.960 +it's gonna say oh it's news request + +00:19:36.960 --> 00:19:38.400 +group what happens has to happen with + +00:19:38.400 --> 00:19:39.280 +news request group + +00:19:39.280 --> 00:19:40.799 +is we take the news command method and + +00:19:40.799 --> 00:19:43.200 +we're going to move it up to the front + +00:19:43.200 --> 00:19:46.240 +to the first argument here and it's + +00:19:46.240 --> 00:19:47.520 +either going to be + +00:19:47.520 --> 00:19:48.720 +it's either going to be given or it's + +00:19:48.720 --> 00:19:50.840 +going to be nil because it's it is + +00:19:50.840 --> 00:19:52.080 +optional + +00:19:52.080 --> 00:19:54.320 +okay I briefly edited the space time + +00:19:54.320 --> 00:19:55.760 +continuum there to conceal the fact that + +00:19:55.760 --> 00:19:56.400 +I had + +00:19:56.400 --> 00:19:57.679 +actually not finished writing the code + +00:19:57.679 --> 00:19:59.440 +that I was supposed to write anyway + +00:19:59.440 --> 00:20:02.159 +um so now we have once we've reordered + +00:20:02.159 --> 00:20:02.960 +the + +00:20:02.960 --> 00:20:04.320 +the arguments to the function then we + +00:20:04.320 --> 00:20:05.760 +have to check our various possible + +00:20:05.760 --> 00:20:06.880 +values one is + +00:20:06.880 --> 00:20:08.640 +uh that the server was not passed in in + +00:20:08.640 --> 00:20:10.080 +which case we recall + +00:20:10.080 --> 00:20:12.400 +request group with the server um the + +00:20:12.400 --> 00:20:13.840 +other is that it's just a string in + +00:20:13.840 --> 00:20:15.360 +which case we do that and then this is + +00:20:15.360 --> 00:20:16.559 +sort of the the normal + +00:20:16.559 --> 00:20:18.559 +the normal case that we would expect to + +00:20:18.559 --> 00:20:20.720 +cons so that's not that bad it's not you + +00:20:20.720 --> 00:20:21.039 +know + +00:20:21.039 --> 00:20:23.760 +it's not beautiful um I would be sort of + +00:20:23.760 --> 00:20:24.480 +ashamed to + +00:20:24.480 --> 00:20:26.159 +let anybody see that particular macro + +00:20:26.159 --> 00:20:28.000 +but I think that it would work okay + +00:20:28.000 --> 00:20:30.640 +now the more difficult thing is going to + +00:20:30.640 --> 00:20:31.440 +be + +00:20:31.440 --> 00:20:34.640 +the data variables so + +00:20:34.640 --> 00:20:37.600 +the equivalent of def vu because our two + +00:20:37.600 --> 00:20:39.360 +options for defining classes here are + +00:20:39.360 --> 00:20:41.039 +def struct and def class both of which + +00:20:41.039 --> 00:20:41.919 +required you + +00:20:41.919 --> 00:20:45.280 +to define the slots inside this macro + +00:20:45.280 --> 00:20:46.960 +itself + +00:20:46.960 --> 00:20:49.039 +so defu is top level um how do we get + +00:20:49.039 --> 00:20:51.280 +the top level this top level macro + +00:20:51.280 --> 00:20:55.039 +uh to insert slot names into these + +00:20:55.039 --> 00:20:56.240 +definitions it's + +00:20:56.240 --> 00:20:58.960 +it's possible that it'll be um that I + +00:20:58.960 --> 00:21:00.240 +could monkey patch + +00:21:00.240 --> 00:21:03.039 +uh an existing struct or an existing + +00:21:03.039 --> 00:21:04.799 +class to add a new slot into it that + +00:21:04.799 --> 00:21:05.280 +sounds + +00:21:05.280 --> 00:21:07.760 +ugly the other option would be to give + +00:21:07.760 --> 00:21:09.600 +it a server variable slot which is just + +00:21:09.600 --> 00:21:11.520 +a generalized bucket + +00:21:11.520 --> 00:21:13.760 +that holds anything that gets defined + +00:21:13.760 --> 00:21:15.520 +via def loop + +00:21:15.520 --> 00:21:16.720 +I don't like either of those solutions + +00:21:16.720 --> 00:21:18.799 +but I'm I don't see any other + +00:21:18.799 --> 00:21:22.480 +any other way of doing that so we re + +00:21:22.480 --> 00:21:25.520 +rewrite the nno declare macro to either + +00:21:25.520 --> 00:21:27.440 +be a destructor or a def class + +00:21:27.440 --> 00:21:29.840 +and we rewrite the def boom macro to + +00:21:29.840 --> 00:21:31.039 +somehow + +00:21:31.039 --> 00:21:33.039 +associate that variable name the symbol + +00:21:33.039 --> 00:21:34.480 +with the with the resulting class + +00:21:34.480 --> 00:21:36.159 +definition + +00:21:36.159 --> 00:21:37.760 +then the last question is do we use + +00:21:37.760 --> 00:21:39.600 +structure classes + +00:21:39.600 --> 00:21:41.600 +they both got their their strengths and + +00:21:41.600 --> 00:21:43.200 +their weaknesses + +00:21:43.200 --> 00:21:46.480 +the nice thing is that I mean I've got + +00:21:46.480 --> 00:21:47.520 +how many servers you're going to have + +00:21:47.520 --> 00:21:49.600 +really I've got I think less than 10 + +00:21:49.600 --> 00:21:51.919 +uh truly deranged mine might have as as + +00:21:51.919 --> 00:21:52.960 +many as + +00:21:52.960 --> 00:21:55.440 +50 let's double that to 100 100 of + +00:21:55.440 --> 00:21:56.480 +anything is not going to matter it + +00:21:56.480 --> 00:21:58.400 +doesn't matter what we use + +00:21:58.400 --> 00:22:00.159 +death structures are simpler they're + +00:22:00.159 --> 00:22:02.720 +lighter weight they're defined on top of + +00:22:02.720 --> 00:22:05.600 +the direct the c records so you know + +00:22:05.600 --> 00:22:06.960 +that's nice + +00:22:06.960 --> 00:22:08.559 +the slots don't carry very much + +00:22:08.559 --> 00:22:10.320 +information with them there's no type + +00:22:10.320 --> 00:22:11.760 +information there's no doc string for + +00:22:11.760 --> 00:22:14.480 +the slots themselves + +00:22:14.480 --> 00:22:16.559 +they can also only do single inheritance + +00:22:16.559 --> 00:22:17.919 +which some might say + +00:22:17.919 --> 00:22:21.120 +was an advantage def class each slot + +00:22:21.120 --> 00:22:22.640 +gets a lot more information associated + +00:22:22.640 --> 00:22:24.000 +with it with it which I think can be + +00:22:24.000 --> 00:22:24.480 +nice + +00:22:24.480 --> 00:22:27.120 +it can do multiple inheritance if you're + +00:22:27.120 --> 00:22:28.799 +going to go there + +00:22:28.799 --> 00:22:30.720 +they are heavier weight in particular + +00:22:30.720 --> 00:22:32.640 +their printed representation is gross + +00:22:32.640 --> 00:22:34.080 +it's enormous + +00:22:34.080 --> 00:22:35.840 +so if you see one show up in a back + +00:22:35.840 --> 00:22:37.520 +trace or in your messages buffer can + +00:22:37.520 --> 00:22:38.240 +really + +00:22:38.240 --> 00:22:39.520 +it can really blow that up and make it + +00:22:39.520 --> 00:22:41.360 +hard to read this of course won't be an + +00:22:41.360 --> 00:22:43.200 +issue because our code won't have any + +00:22:43.200 --> 00:22:46.240 +errors in it um my argument for multiple + +00:22:46.240 --> 00:22:48.320 +inheritance here is that I can imagine + +00:22:48.320 --> 00:22:51.280 +new servers falling into sort of like a + +00:22:51.280 --> 00:22:52.720 +little two by two matrix of + +00:22:52.720 --> 00:22:56.240 +of parent classes one being news versus + +00:22:56.240 --> 00:22:56.799 +mail + +00:22:56.799 --> 00:23:00.320 +so news the messages belong to somebody + +00:23:00.320 --> 00:23:00.720 +else + +00:23:00.720 --> 00:23:02.080 +you can't touch them you can't delete + +00:23:02.080 --> 00:23:03.840 +them mail meaning + +00:23:03.840 --> 00:23:06.000 +the messages are under your command + +00:23:06.000 --> 00:23:08.960 +either a local mail dealer a remote imap + +00:23:08.960 --> 00:23:11.039 +you're allowed to spool them copy them + +00:23:11.039 --> 00:23:12.640 +delete them at will + +00:23:12.640 --> 00:23:13.919 +and then the other sort of line of the + +00:23:13.919 --> 00:23:16.400 +matrix would be a local file system + +00:23:16.400 --> 00:23:19.760 +versus some kind of a you know server + +00:23:19.760 --> 00:23:20.559 +port + +00:23:20.559 --> 00:23:23.280 +remote access and that second the server + +00:23:23.280 --> 00:23:24.960 +port remote access thing might require + +00:23:24.960 --> 00:23:26.880 +authentication it might require a keep + +00:23:26.880 --> 00:23:28.559 +alive for a connection + +00:23:28.559 --> 00:23:30.159 +um it's there's going to be a process + +00:23:30.159 --> 00:23:31.600 +there rather than just file system + +00:23:31.600 --> 00:23:32.400 +commands + +00:23:32.400 --> 00:23:33.840 +so I could see if I was going to do + +00:23:33.840 --> 00:23:35.360 +multiple inheritance that's what I would + +00:23:35.360 --> 00:23:36.240 +do those two + +00:23:36.240 --> 00:23:39.039 +those two possible parent classes anyway + +00:23:39.039 --> 00:23:40.400 +that's as far as I've gotten + +00:23:40.400 --> 00:23:41.520 +I thought that I would be able to write + +00:23:41.520 --> 00:23:43.279 +more of this code before I did this talk + +00:23:43.279 --> 00:23:44.720 +but instead I spent the whole time + +00:23:44.720 --> 00:23:46.720 +messing with video codecs but that's + +00:23:46.720 --> 00:23:48.320 +where we're at and I'm going to cut + +00:23:48.320 --> 00:23:49.440 +myself off now + +00:23:49.440 --> 00:23:50.960 +I hope there are questions I hope I'm + +00:23:50.960 --> 00:23:53.440 +there to to answer your questions + +00:23:53.440 --> 00:23:55.919 +and thanks very much again to everyone + +00:23:55.919 --> 00:23:57.120 +involved + +00:23:57.120 --> 00:23:59.279 +bye |