path: root/2021/captions/emacsconf-2021-janitor--a-day-in-the-life-of-a-janitor--stefan-monnier--main.vtt

WEBVTT

00:01.520 --> 00:04.400
Hello, my name is Stefan Monnier,

00:04.400 --> 00:06.799
and I'm going to talk to you about--

00:06.799 --> 00:08.240
well, I'm going to present a bit

00:08.240 --> 00:11.840
of the life of a janitor.

00:11.840 --> 00:14.050
So by and large, there's just

00:14.050 --> 00:16.299
nothing to see here,

00:16.299 --> 00:17.199
and that's probably

00:17.199 --> 00:18.240
not super interesting,

00:18.240 --> 00:19.920
but some of you might actually like to

00:19.920 --> 00:00:23.050
see how I work, so I figured why not.

00:25.359 --> 00:27.279
Usually what I do just doesn't make any

00:27.279 --> 00:00:29.920
any significant difference, 

00:00:29.920 --> 00:00:32.160
and so I basically take existing code

00:00:32.160 --> 00:00:35.040
that's working, and I try to change it

00:00:35.040 --> 00:00:37.680
hopefully without breaking it too much

00:00:37.680 --> 00:00:40.079
and make it slightly more...

00:40.079 --> 00:42.719
you know, following some of the more

00:42.719 --> 00:44.640
modern style, let's say,

00:44.640 --> 00:00:46.719
and sometimes along the way, 

00:00:46.719 --> 00:00:50.399
it actually fixes some bugs.

00:50.399 --> 00:00:51.983
More concretely, the kind of things 

00:00:51.983 --> 00:00:54.079
that I do is basically activate 

00:00:54.079 --> 00:00:54.480
lexical scoping--

00:54.480 --> 00:56.239
that's really my main goal usually--

00:56.239 --> 00:58.960
but also do things like convert

00:58.960 --> 00:01:00.719
from `cl` to `cl-lib`, 

00:01:00.719 --> 00:01:01.440
sometimes I have to

01:01.440 --> 01:03.760
fix some compilation dependencies,

01:03.760 --> 01:07.280
I might convert from `defadvice` to `advice-add`,

01:07.280 --> 01:11.439
and many of the things--

01:11.439 --> 00:01:13.119
in terms of number of changes, 

00:01:13.119 --> 00:01:14.000
most of them are actually 

00:01:14.000 --> 00:01:16.560
changing `quote fun` to `hash quote fun` 

00:01:16.560 --> 00:01:17.360
because I prefer it,

01:17.360 --> 00:01:19.920
but also it often helps me 

00:01:19.920 --> 00:01:21.439
have a better understanding 

00:01:21.439 --> 00:01:23.920
of which function is called where,

01:23.920 --> 01:26.799
and so the warnings I get from it

01:26.799 --> 01:28.799
sometimes help me.  You look concretely...

01:28.799 --> 00:01:30.880
it's not nothing really clear; 

00:01:30.880 --> 00:01:33.360
it's more in terms of helping me 

00:01:33.360 --> 00:01:35.759
have a mental image 

00:01:35.759 --> 00:01:39.439
of how the package works.

01:39.439 --> 01:42.880
So let's take a look.

01:42.880 --> 00:01:45.840
I'm going to start with 

00:01:45.840 --> 00:01:46.799
the package `heap`, 

00:01:46.799 --> 00:01:50.560
which I saw had a few weird things in it,

00:01:50.560 --> 00:01:53.680
so I'm going to compile it.

01:53.680 --> 01:55.600
That's basically the way the way I work,

01:55.600 --> 00:01:57.840
right. I take a package. 

00:01:57.840 --> 00:02:00.479
I just pass it to the byte compiler.  

00:02:00.479 --> 00:02:02.159
I do that by just having

02:02.159 --> 02:04.560
a clone of the whole

02:04.560 --> 00:02:06.799
GNU ELPA repository, 

00:02:06.799 --> 00:02:10.000
and so that's why I built them.

02:10.000 --> 02:11.520
I use the build rules 

02:11.520 --> 02:15.120
from the GNU ELPA repository.

02:15.120 --> 00:02:16.720
These build rules enforce-- 

00:02:16.720 --> 00:02:17.680
make sure that the files 

00:02:17.680 --> 00:02:19.680
are compiled in a clean environment 

00:02:19.680 --> 00:02:21.920
so you get fairly good warnings.  

00:02:21.920 --> 00:02:23.680
If you look at the warnings you see here, 

00:02:23.680 --> 00:02:24.720
there's a lot of things 

00:02:24.720 --> 00:02:26.480
which are completely irrelevant, 

00:02:26.480 --> 00:02:28.400
which are due to details 

00:02:28.400 --> 00:02:30.319
of the way I have my Emacs set up

00:02:30.319 --> 00:02:31.599
and some of the local changes 

00:02:31.599 --> 00:02:34.319
I had in it so, you know, 

00:02:34.319 --> 00:02:35.280
there's no point 

00:02:35.280 --> 00:02:37.920
paying too much attention to it,

02:37.920 --> 02:40.400
but here we have a first warning.

02:40.400 --> 02:42.959
We see that this is using `cl`,

02:42.959 --> 02:45.040
so we want to change this to `cl-lib`,

02:45.040 --> 00:02:46.879
but that also means 

00:02:46.879 --> 00:02:48.400
that we may have a new dependency 

00:02:48.400 --> 00:02:49.920
on the `cl-lib` package, 

00:02:49.920 --> 00:02:51.120
so we have to go check 

00:02:51.120 --> 00:02:52.000
the start of the file 

00:02:52.000 --> 00:02:54.080
to see if it already declares

00:02:54.080 --> 00:02:56.800
some dependency, and we see it doesn't,

02:56.800 --> 00:03:00.640
not even on a on a recent-enough Emacs,

00:03:00.640 --> 00:03:02.325
so we have to add-- 

00:03:02.325 --> 00:03:05.360
sorry, that's not going very well...

03:05.360 --> 03:06.480
oh...

03:06.480 --> 03:08.560
okay, we're going to get there somewhere...

03:08.560 --> 03:13.200
somehow...

03:13.200 --> 03:18.020
oh, that still wasn't it, wow, okay--

03:20.480 --> 03:22.159
and along the way...

03:22.159 --> 00:03:24.159
Of course, since we converted to `cl-lib`, 

00:03:24.159 --> 00:03:26.159
we have to update the uses

00:03:26.159 --> 00:03:29.840
so `defstruct` shouldn't be used anymore.

03:29.840 --> 03:31.599
We may want to reindent this

03:31.599 --> 03:36.000
to get something a bit cleaner.

03:37.040 --> 00:03:40.589
We have here a missing quote... 

00:03:40.589 --> 00:03:41.920
hash, sorry.

03:41.920 --> 00:03:46.480
We have `decf`, so `decf` is here,

03:46.480 --> 00:03:48.000
and that needs to be replaced 

00:03:48.000 --> 00:03:49.920
with `cl-decf`. 

00:03:49.920 --> 00:03:51.120
Sometimes it's worth doing 

00:03:51.120 --> 00:03:53.360
a search-and-replace.  

00:03:53.360 --> 00:03:54.799
Here I see there's only two,

00:03:54.799 --> 00:03:57.760
so it's not worth the trouble;

03:57.760 --> 00:04:00.711
I just do it by hand, and that's it.  

00:04:00.711 --> 00:04:02.000
Well, that was easy.

04:02.000 --> 04:05.000
So let's recompile, see what it says.

04:10.159 --> 04:12.959
Ah, this is clean.  Perfect!

04:12.959 --> 04:15.000
Let's.. we can go see...

04:15.000 --> 04:17.280
There is another one I had.

04:17.280 --> 04:20.239
Was it `counsel`, I think.  Yes.

04:20.239 --> 00:04:24.160
So also I saw some funny things

00:04:24.160 --> 00:04:24.320
going on here.

04:24.320 --> 00:04:26.479
So I'm going to do 

00:04:26.479 --> 00:04:31.040
the same procedure as before: 

00:04:31.040 --> 00:04:32.800
I just compile the file

00:04:32.800 --> 00:04:35.000
and look at the warnings.

04:38.000 --> 04:40.479
Oh, we have many more here.

04:40.479 --> 04:43.120
So let's see...

04:43.120 --> 00:04:46.504
Okay, so we have missing quotes-- 

00:04:46.504 --> 00:04:49.240
oh, hashes. They're not really missing;

04:49.240 --> 04:54.639
it's just a personal preference.

04:54.639 --> 04:57.440
Oh, here... here's an important one:

04:57.440 --> 04:59.280
so as you know,

04:59.280 --> 05:00.639
if you look at the top of the file,

05:00.639 --> 00:05:02.240
you see that here 

00:05:02.240 --> 00:05:04.960
it says it's using lexical binding,

05:04.960 --> 05:07.120
yet it's not fully using lexical binding,

05:07.120 --> 00:05:08.960
because as we just saw, 

00:05:08.960 --> 00:05:11.039
there's a call to the `eval` function 

00:05:11.039 --> 00:05:11.680
with only one argument,

05:11.680 --> 05:13.280
which means the second argument is nil,

05:13.280 --> 05:16.880
which means that the expression read

05:16.880 --> 00:05:19.520
by `read` here is going to be evaluated

05:19.520 --> 00:05:22.160
using the old dialects, 

00:05:22.160 --> 00:05:24.240
which is only dynamic scoping.  

00:05:24.240 --> 00:05:25.680
So here I like to just change this

00:05:25.680 --> 00:05:26.800
to use lexical scoping,

05:26.800 --> 00:05:28.080
which in most cases 

00:05:28.080 --> 00:05:29.680
just doesn't make any difference.

00:05:29.680 --> 00:05:30.870
It just makes me feel better.

05:35.919 --> 05:40.160
So there's lots of those hashes

05:40.160 --> 05:41.759
all over the place.

05:43.680 --> 05:45.680
It's not strictly necessary, as you know,

05:45.680 --> 05:51.500
but I'm just going to add them anyway.

05:52.479 --> 00:05:53.199
Here we see 

00:05:53.199 --> 00:05:54.800
it's not going to warn me here

00:05:54.800 --> 00:05:55.759
because it doesn't know 

00:05:55.759 --> 00:05:57.600
that `ivy-make-magic-action` 

00:05:57.600 --> 00:05:58.400
takes a function, 

00:05:58.400 --> 00:06:02.319
but it's a pretty good guess that it does.

06:12.319 --> 06:14.479
And here's some more.

06:14.479 --> 06:16.080
What else do we have?

06:16.080 --> 06:19.120
Is that all we have here?

06:19.120 --> 06:21.440
Well, looks like it.  Oh, I see a few...

06:21.440 --> 06:27.680
a few more here...

06:27.680 --> 06:30.639
and one more.

06:30.639 --> 06:33.039
And oh, this is more interesting.

06:33.039 --> 06:35.280
So here we have a use of `defadvice`,

06:35.280 --> 06:37.440
so if we go back

06:37.440 --> 06:38.479
to the beginning of the file,

06:40.720 --> 06:42.880
we see that it actually depends

06:42.880 --> 00:06:47.360
on Emacs 24.5, so it actually has

06:47.360 --> 00:06:49.280
the new advice system available 

00:06:49.280 --> 00:06:51.520
without having to add any dependency, 

00:06:51.520 --> 00:06:53.599
so there's really no good reason 

00:06:53.599 --> 00:06:54.880
to keep this.

06:54.880 --> 00:06:56.160
So we just convert this 

00:06:56.160 --> 00:06:58.560
to an `advice-add`,

06:58.560 --> 00:06:59.840
so it just says, you know, 

00:06:59.840 --> 00:07:02.319
this is the function that's advised.

07:02.319 --> 07:04.560
This was a `before` advice.

07:04.560 --> 07:05.500
The `before` advice, sometimes,

07:05.500 --> 07:08.479
when we convert it to `advice-add`,

07:08.479 --> 07:11.199
need to be converted to `around` advice.

07:11.199 --> 07:13.280
This is when the function

07:13.280 --> 07:15.840
looks or modifies the argument.

07:15.840 --> 07:18.639
In this case, if I look at it,

07:18.639 --> 07:20.319
I see it doesn't seem to be using

07:20.319 --> 07:21.280
the arguments at all.

07:21.280 --> 00:07:25.280
So I'm just going to keep it

00:07:25.280 --> 00:07:27.520
as a `before` advice.

07:27.520 --> 00:07:28.672
And we have to give it a name.

00:07:28.672 --> 00:07:30.880
Well, we don't really have to,

07:30.880 --> 07:32.800
but it's convenient to give it a name

07:32.800 --> 07:34.800
to the new function.

07:34.800 --> 00:07:36.880
So here, they actually had 

00:07:36.880 --> 00:07:38.080
given a name to the advice, 

00:07:38.080 --> 00:07:39.599
so we're going to keep it, 

00:07:39.599 --> 00:07:41.440
and indeed it's the only function.

00:07:41.440 --> 00:07:43.360
This name is not used as a function,

00:07:43.360 --> 00:07:44.160
so we can use it 

00:07:44.160 --> 00:07:46.960
as the name of the function.

07:46.960 --> 00:07:49.039
I'm going to add a dash here 

00:07:49.039 --> 00:07:51.120
because I think this function 

00:07:51.120 --> 00:07:53.039
is really fundamentally 

00:07:53.039 --> 00:07:54.639
an internal function.

07:54.639 --> 07:56.720
So here I just said I add the advice,

07:56.720 --> 07:58.000
but I still need to actually

07:58.000 --> 07:59.800
define the function.

08:02.879 --> 00:08:04.160
So that's what I do here, 

00:08:04.160 --> 00:08:06.500
and we need here to list the arguments

08:06.500 --> 08:08.240
that are going to be taken.

08:08.240 --> 00:08:09.199
I don't know what these are, 

00:08:09.199 --> 00:08:10.960
but I know we're not using them, 

00:08:10.960 --> 00:08:13.759
so we'll just accept anything,

08:13.759 --> 08:16.560
and that will do the trick.

08:16.560 --> 08:19.199
It's a future-proof as well,

08:19.199 --> 08:22.240
so that should work.

08:22.240 --> 00:08:24.160
Oh, here we have another, so it's 

00:08:24.160 --> 00:08:29.919
basically the same story, I think.

08:29.919 --> 00:08:31.599
It's a `before` advice as well.  

00:08:31.599 --> 00:08:32.959
It doesn't seem to be using

00:08:32.959 --> 00:08:35.599
the argument at all,

08:35.599 --> 00:08:38.596
and let's see if this name is not taken.

00:08:38.596 --> 00:08:43.360
Yeah, good, so we can just do the same:

08:43.360 --> 08:46.880
turn this into an `advice-add`...

08:46.880 --> 08:48.300
`before`...

08:53.040 --> 08:55.000
I just add a dash here.

09:02.480 --> 00:09:05.440
And same thing-- 

00:09:05.440 --> 00:09:06.959
a function that just takes...

09:06.959 --> 09:08.240
because I don't know which arguments

09:08.240 --> 09:10.480
these are so...

09:10.480 --> 09:14.640
I think that should do the trick.

09:14.640 --> 00:09:16.080
Actually, we see that this function 

00:09:16.080 --> 00:09:18.560
is very similar to the other one.

09:18.560 --> 09:23.000
Let's look at the two side-by-side...

09:31.519 --> 00:09:33.055
...it really is-- 

00:09:33.055 --> 00:09:36.097
oh, it's not exactly identical... 

00:09:36.097 --> 00:09:39.120
it's, you know, we could try

09:39.120 --> 09:41.680
to merge them into a single function,

09:41.680 --> 09:43.279
but it's probably not worth the trouble

09:43.279 --> 09:45.920
so we can keep it this way.

09:45.920 --> 09:48.720
Okay, next warning: an `eval` again,

09:48.720 --> 09:50.640
so I could just add `t` here,

09:50.640 --> 00:09:55.120
but if you look at it a bit more, 

00:09:55.120 --> 00:09:56.000
you see that the code 

00:09:56.000 --> 00:09:57.760
we're going to evaluate

09:57.760 --> 00:09:59.279
using either lexical scoping 

00:09:59.279 --> 00:10:00.560
or dynamic scoping 

00:10:00.560 --> 00:10:03.440
is actually just evaluating a symbol,

00:10:03.440 --> 00:10:06.240
since we just call an `intern` here.

10:06.240 --> 00:10:07.839
So instead of replacing this 

00:10:07.839 --> 00:10:09.279
by adding an argument, 

00:10:09.279 --> 00:10:11.680
I'm just going to call `symbol-value` 

00:10:11.680 --> 00:10:12.640
because that's exactly 

00:10:12.640 --> 00:10:14.480
what we need to do here, right.  

00:10:14.480 --> 00:10:16.320
I call this "strength reduction," 

00:10:16.320 --> 00:10:17.200
and I'm using 

00:10:17.200 --> 00:10:19.680
a more primitive function instead, 

00:10:19.680 --> 00:10:23.200
which does just what we need,

10:23.200 --> 10:25.680
and this one knows that it has to be

10:25.680 --> 00:10:30.640
accessed by dynamic scoping, of course.

10:30.640 --> 00:10:32.959
Here I have a `kmacro-ring`, 

00:10:32.959 --> 00:10:35.600
so here I have a function that uses--

10:35.600 --> 00:10:37.360
`kmacro-ring` comes from

00:10:37.360 --> 00:10:39.760
the `kmacro` package, obviously,

10:39.760 --> 10:41.600
and we probably don't want to

10:41.600 --> 10:42.959
`require` `kmacro` package

10:42.959 --> 00:10:48.560
all over the place in `counsel` itself,

10:48.560 --> 00:10:50.240
because `counsel` can be used 

00:10:50.240 --> 00:10:53.279
without `kmacro`.

10:53.279 --> 00:10:55.200
So I think we're just going to add 

00:10:55.200 --> 00:11:04.000
a `defvar` to silence the warning.

11:05.519 --> 00:11:10.720
And we have several more. So we have

11:10.720 --> 00:11:14.000
`initial-counter-value`. (Sorry.)

11:20.480 --> 11:23.360
We have `kmacro-counter`.

11:23.360 --> 11:25.760
Do we have more?

11:25.760 --> 11:28.560
Oh, yes, we do.

11:28.560 --> 11:35.040
We have `kmacro-counter-value-start`

11:35.040 --> 11:40.839
and `kmacro-counter-format-start`.

11:40.839 --> 11:43.920
Okay.

11:45.040 --> 11:50.160
I hope this is it.

11:50.160 --> 11:52.880
`kmacro-ring`, `counter`, `ring`...

11:52.880 --> 11:54.959
blah blah blah.

11:54.959 --> 00:12:00.240
Here we have another one, `quote`.

12:00.240 --> 12:03.279
Here we have another hash missing.

12:03.279 --> 12:06.079
It's not missing...

12:06.079 --> 12:08.000
but same thing here.

12:12.079 --> 00:12:16.560
Okay, this is a function from `kmacro`.

12:16.560 --> 00:12:18.079
We could declare it 

00:12:18.079 --> 00:12:20.880
just to silence the warning

12:20.880 --> 00:12:22.320
although we don't actually... 

00:12:22.320 --> 00:12:24.480
normally, when we declare such things--

12:24.480 --> 00:12:25.279
same thing with variables-- 

00:12:25.279 --> 00:12:27.300
we should try to make sure that indeed

12:27.300 --> 12:28.760
by the time the code is executed,

12:28.760 --> 12:30.800
the function will be available,

12:30.800 --> 00:12:32.800
and then very often is 

00:12:32.800 --> 00:12:34.320
because there's a `require` 

00:12:34.320 --> 00:12:35.680
sometimes inside a function, 

00:12:35.680 --> 00:12:36.399
and so we should put 

00:12:36.399 --> 00:12:37.680
the `declare` function 

00:12:37.680 --> 00:12:39.920
right after the `require`, 

00:12:39.920 --> 00:12:41.839
but I don't think it's the case here.

12:41.839 --> 00:12:46.399
So I'm just going to to add this.

12:46.399 --> 12:49.040
I know this comes from `kmacro`,

12:49.040 --> 00:12:53.500
and I could actually check the arguments.

12:56.320 --> 00:12:58.480
It's just taking an optional argument 

00:12:58.480 --> 00:13:00.880
so I'm going to put it there, 

00:13:00.880 --> 00:13:06.720
so we have it complete.

13:06.720 --> 13:10.800
Okay, we can just recompile,

13:10.800 --> 00:13:14.800
see what is left 

00:13:14.800 --> 00:13:17.760
from those warnings we've fixed, 

00:13:17.760 --> 00:13:21.360
and we may have new warnings, in any case, 

00:13:21.360 --> 00:13:25.440
because especially when we add the hashes,

00:13:25.440 --> 00:13:29.519
it tends to give us more warnings.

13:29.519 --> 00:13:31.200
So we have two more functions 

00:13:31.200 --> 00:13:34.560
which are not known.

13:34.560 --> 13:39.440
You can just add them here...

13:39.440 --> 13:44.720
`set-format "kmacro"`

13:44.720 --> 13:48.160
and same thing for `set-counter`.

13:48.160 --> 13:50.000
Okay, whatever.

13:54.959 --> 00:13:57.120
This just takes a `format` argument, 

00:13:57.120 --> 00:14:05.920
and this one just takes an `arg` argument.

14:05.920 --> 14:10.800
Okay, so let's see what this says now.

14:10.800 --> 14:15.519
Hopefully, there's no warnings anymore.

14:15.519 --> 14:17.839
We're done.  Okay!

14:17.839 --> 00:14:20.079
Okay, the last one we're going to see 

00:14:20.079 --> 00:14:23.440
is in `enwc`, I saw the other day...

14:23.440 --> 14:26.240
I think I have it here...

14:27.760 --> 14:29.680
here we go, yes...

14:29.680 --> 14:32.800
so `enwc` is an interesting package here

14:32.800 --> 14:35.680
because it has-- as you can see it has--

14:35.680 --> 14:37.760
it's lexical binding,

14:37.760 --> 14:39.760
but actually some of the files in it

14:39.760 --> 14:42.320
do not use lexical binding,

14:42.320 --> 14:44.320
so it has been partly converted

14:44.320 --> 14:46.160
but not completely.

14:46.160 --> 00:14:49.920
So here I'm going to 

00:14:49.920 --> 00:14:54.160
enable lexical binding.

14:54.160 --> 14:58.880
I have also, I think, in `cm`...

14:58.880 --> 15:01.199
yes...

15:01.199 --> 15:04.000
so I enable it here,

15:04.000 --> 15:07.360
and also, I think, `test`.

15:07.360 --> 00:15:09.360
The test files are often 

00:15:09.360 --> 00:15:11.839
somewhat problematic 

00:15:11.839 --> 00:15:15.199
because very often they're not quite

15:15.199 --> 15:18.880
as heavily tested themselves, actually,

15:18.880 --> 00:15:20.320
or they only run 

00:15:20.320 --> 00:15:22.160
in very specific contexts, 

00:15:22.160 --> 00:15:24.399
and so they may have problems 

00:15:24.399 --> 00:15:27.360
with missing `requires` or using packages 

00:15:27.360 --> 00:15:29.199
which are not explicitly in the dependencies

15:29.199 --> 15:31.279
and those kinds of things.

15:31.279 --> 15:33.360
I think this is not the case here,

15:33.360 --> 15:35.440
but we'll see.

15:35.440 --> 15:38.880
`enwc`...

15:38.880 --> 15:42.320
Yes, I want to save this one and that one.

15:42.320 --> 15:45.000
Let's see what it says.

15:47.199 --> 15:51.440
Okay, unused lexical variable `x`...

15:51.440 --> 15:52.240
`x`...

15:52.240 --> 15:57.120
Yes, so here we have an unused variable,

15:57.120 --> 15:58.320
and indeed, it's not used.

15:58.320 --> 16:00.880
It probably had to be named before

16:00.880 --> 16:04.079
because it was...

16:04.079 --> 00:16:05.120
with dynamic scoping, 

00:16:05.120 --> 00:16:06.399
the `dotimes` requires 

00:16:06.399 --> 00:16:08.160
the variable to be named, actually, 

00:16:08.160 --> 00:16:10.399
because it's used internally somehow,

16:10.399 --> 00:16:11.600
but with lexical scoping, 

00:16:11.600 --> 00:16:12.320
that's not the case,

00:16:12.320 --> 00:16:14.079
so we can just put an underscore.

16:14.079 --> 00:16:15.199
I'm going to change this 

00:16:15.199 --> 00:16:16.880
because I really don't like

16:16.880 --> 16:19.000
this three-part `dotimes`.

16:19.000 --> 00:16:21.360
I prefer to have 

00:16:21.360 --> 00:16:23.040
the return value at the end.

16:23.040 --> 00:16:26.480
It's sort of stashed hidden in the middle.

16:26.480 --> 16:29.680
That's just a personal preference.

16:29.680 --> 16:31.920
Okay, what else... we have a `widget`.

16:31.920 --> 16:34.000
Okay, this argument here says that

16:34.000 --> 16:37.000
it's not used, so if we look at...

16:44.320 --> 00:16:47.040
We were here, right?  Yes. Right here.  

00:16:47.040 --> 00:16:50.480
Indeed, `widget` is really not used.

16:50.480 --> 16:51.230
(Sorry.)

16:53.600 --> 00:16:55.279
Here's what I get for using 

00:16:55.279 --> 00:16:58.320
a somewhat vanilla configuration of Emacs,

16:58.320 --> 17:01.279
compared to the one I use...

17:01.279 --> 17:04.000
the personally tricked one.

17:04.000 --> 17:05.439
Actually, I can...

17:05.439 --> 17:07.919
so we can just mark this argument

17:07.919 --> 17:09.360
as unused,

17:09.360 --> 17:11.199
and we don't want to remove the argument

17:11.199 --> 00:17:12.480
probably, or maybe we could; 

00:17:12.480 --> 00:17:15.679
we could see where the function is used,

17:15.679 --> 00:17:18.542
and here we see that it's passed

00:17:18.542 --> 00:17:20.959
to a higher-order function,

17:20.959 --> 17:24.480
basically, so it's going to be...

17:24.480 --> 00:17:25.360
We can't really change 

00:17:25.360 --> 00:17:25.760
the calling convention

17:25.760 --> 17:27.120
so we have to mark the argument

17:27.120 --> 17:29.600
as being just an unused argument,

17:29.600 --> 17:34.000
but we're going to still receive it.

17:34.000 --> 00:17:35.360
And here it says same thing: 

00:17:35.360 --> 00:17:38.240
that `widget` is not used in this function.

17:38.240 --> 17:40.000
Let's take a look at the function.

17:40.000 --> 17:42.400
Indeed it seems it's not used,

17:42.400 --> 17:44.000
and so we're just going to mark it

17:44.000 --> 17:46.480
as unused.

17:46.480 --> 00:17:48.320
This is the part of the conversion

00:17:48.320 --> 00:17:49.200
to lexical scoping

00:17:49.200 --> 00:17:51.280
that's somewhat tricky sometimes

00:17:51.280 --> 00:17:53.760
because we don't really know 

00:17:53.760 --> 00:17:56.240
whether this variable should be using

00:17:56.240 --> 00:17:58.559
lexical scoping or dynamic scoping.

17:58.559 --> 00:18:00.480
The fact that it's not used 

00:18:00.480 --> 00:18:02.320
is a hint that there's probably 

00:18:02.320 --> 00:18:03.679
something going on,

18:03.679 --> 00:18:04.960
so either it's not used 

00:18:04.960 --> 00:18:06.400
because it should be using 

00:18:06.400 --> 00:18:07.200
dynamic scoping-- 

00:18:07.200 --> 00:18:08.080
it is going to be used 

00:18:08.080 --> 00:18:10.480
by some other code somewhere else--

18:10.480 --> 00:18:11.840
or it's really not used

00:18:11.840 --> 00:18:14.000
because it's just not used, right,

00:18:14.000 --> 00:18:16.320
and so we need to distinguish the two, 

00:18:16.320 --> 00:18:20.880
and for that, I basically use 

00:18:20.880 --> 00:18:22.240
my own judgment.

18:22.240 --> 18:24.880
This is based typically on the fact that

18:24.880 --> 00:18:27.760
this is just a very short name, 

00:18:27.760 --> 00:18:32.000
and most local identifiers use short names,

18:32.000 --> 18:34.400
whereas item values used for dynamic scoping

18:34.400 --> 18:36.720
typically have a package prefix

18:36.720 --> 00:18:37.679
or something like this.  

00:18:37.679 --> 00:18:38.960
So the fact that it's a short name

00:18:38.960 --> 00:18:40.880
gives me a good idea.

18:40.880 --> 00:18:41.520
Here in this case, 

00:18:41.520 --> 00:18:42.640
I actually look at the code, 

00:18:42.640 --> 00:18:45.600
and we see that there's nothing in here

18:45.600 --> 00:18:47.039
that may actually refer 

00:18:47.039 --> 00:18:48.080
to this variable `widget`, 

00:18:48.080 --> 00:18:49.280
so I think it's safe,

18:49.280 --> 00:18:51.360
but in the general case, 

00:18:51.360 --> 00:18:54.400
we may look here and be surprised,

18:54.400 --> 00:18:55.760
or, you know, you may call out 

00:18:55.760 --> 00:18:58.320
the functions which may themselves end up

18:58.320 --> 19:00.080
referring to this variable.

19:00.080 --> 19:02.640
So sometimes we need to investigate a

19:02.640 --> 19:03.840
little more.

19:03.840 --> 19:05.919
We are most of the time not completely sure

19:05.919 --> 19:07.520
whether the result is correct or not,

19:07.520 --> 00:19:09.520
of course, so the other thing 

00:19:09.520 --> 00:19:10.640
you may want to check 

00:19:10.640 --> 00:19:12.160
is also uses of things 

00:19:12.160 --> 00:19:14.400
like `eval` or `symbol-value`.

19:14.400 --> 19:17.200
So it's often a good idea to search,

19:17.200 --> 00:19:18.799
and you do a search of `eval`, 

00:19:18.799 --> 00:19:21.490
and you see here it's using `eval`.  

00:19:21.490 --> 00:19:24.160
Hmmm... Okay, so what does this `eval` do?

19:24.160 --> 00:19:25.760
It's evaluating expressions 

00:19:25.760 --> 00:19:28.240
that appear in `args` here

19:28.240 --> 19:31.840
so you can see where those args come from,

19:31.840 --> 00:19:35.120
and we see here, these are expressions 

00:19:35.120 --> 00:19:36.840
that don't do anything very special.

19:36.840 --> 19:41.520
It's just using `make-supplicant-choice`,

19:41.520 --> 19:44.960
and `make-supplicant-choice` itself

19:44.960 --> 19:47.120
just doesn't refer to `widget`, for example,

19:47.120 --> 19:50.000
so you know we should be safe,

19:50.000 --> 19:52.559
but while I'm here...

19:52.559 --> 19:53.840
okay, well, then we can do that later.

19:53.840 --> 19:55.679
Well, that's actually the next warning,

19:55.679 --> 00:19:58.080
exactly. So here we see that this is 

00:19:58.080 --> 00:20:00.000
using the dynamically-scoped dialect,

00:20:00.000 --> 00:20:02.799
so we convert it to lexical-scoped.

20:02.799 --> 20:04.559
Of course, this may introduce errors,

20:04.559 --> 20:07.200
but we hope it doesn't.

20:07.200 --> 20:08.880
And actually, it was a good change here,

20:08.880 --> 20:12.080
because if you see again,

20:12.080 --> 00:20:14.240
this actually evals expressions

00:20:14.240 --> 00:20:16.159
that appear here in `args`,

20:16.159 --> 20:18.480
and so these are expressions

20:18.480 --> 20:21.039
that are passed here.

20:21.039 --> 20:23.679
So this expression here used to be

20:23.679 --> 00:20:24.480
evaluated with dynamic scoping, 

00:20:24.480 --> 00:20:28.000
even though it appears to be normal code

00:20:28.000 --> 00:20:29.760
within this file, which says 

00:20:29.760 --> 00:20:32.559
it's using lexical scoping,

20:32.559 --> 20:34.400
and so there are some remnants

20:34.400 --> 20:36.640
of dynamic scoping all over the place

20:36.640 --> 00:20:37.840
in Emacs still, because we have

00:20:37.840 --> 00:20:43.679
those calls of `eval` with a nil argument.

20:44.880 --> 20:47.039
Here we have `cons`...

20:47.039 --> 20:50.400
that needs to be `hash quoted`.

20:52.400 --> 00:20:54.080
Oh, and we have a reference 

00:20:54.080 --> 00:20:56.720
to this variable `enwc-edit-id'. 

00:20:56.720 --> 00:20:57.520
So this is clearly 

00:20:57.520 --> 00:21:00.400
a dynamic-scoped variable.

21:00.400 --> 21:02.000
We can either add a `defvar`

21:02.000 --> 21:03.440
to silence the warning,

21:03.440 --> 00:21:06.799
or maybe we can `require` the package.

21:06.799 --> 21:10.080
The file that defines it...

21:14.080 --> 21:17.360
So let's see where it's defined.

21:17.360 --> 21:21.200
Here it's defined in `enwc.el`,

21:21.200 --> 00:21:23.440
so I'm going to try just to add

00:21:23.440 --> 00:21:25.039
the dependency.

21:25.039 --> 00:21:27.840
I'm going to `require` here. This is risky.

21:27.840 --> 21:30.159
We'll see when we compile a file later,

21:30.159 --> 21:32.320
we may get a circular dependency

21:32.320 --> 21:34.720
because of it.

21:34.720 --> 21:36.320
If that's the case, we're going to

21:36.320 --> 00:21:38.320
have to remove this `require` 

00:21:38.320 --> 00:21:42.000
and instead put `defvar`s.

21:42.000 --> 21:42.559
Sometimes it's worth actually

21:42.559 --> 21:44.640
looking further at the various files

21:44.640 --> 00:21:48.080
to see how to redefine the dependencies

21:48.080 --> 21:49.840
to break those circular dependencies,

21:49.840 --> 21:52.320
but it's often not really

21:52.320 --> 21:54.720
worth the trouble.

21:55.679 --> 00:21:58.400
Oh, no, that's not what-- 

00:21:58.400 --> 00:22:01.440
I'm not going to the right place... 

00:22:01.440 --> 00:22:07.039
Here I was. So here `edit-map`.

22:07.039 --> 22:09.760
Well, we can probably...

22:09.760 --> 22:12.159
it may disappear or...

22:12.159 --> 22:13.760
oh, I see.

22:13.760 --> 22:16.320
Okay, so this `edit-map` actually is

22:16.320 --> 22:18.559
defined in this very file.

22:18.559 --> 00:22:20.240
It's just that it's defined later. 

00:22:20.240 --> 00:22:21.600
So all we need to do 

00:22:21.600 --> 00:22:24.320
is to move this definition

00:22:24.320 --> 00:22:27.200
to before its first use,

22:27.200 --> 22:28.960
since otherwise it's going to be taken

22:28.960 --> 22:33.520
as lexically-scoped, which we don't want.

22:33.520 --> 22:35.360
And while I'm here, I see this `copy-keymap`.

22:35.360 --> 22:38.400
I don't like `copy-keymap`,

22:38.400 --> 22:40.960
so I'm going to change this

22:40.960 --> 22:44.080
to a normal keymap,

22:44.080 --> 22:46.159
and then I'm just going to use

22:46.159 --> 22:50.080
`set-keymap-parent` instead of `copy-keymap`

22:50.080 --> 00:22:51.600
to get basically the same result,

00:22:51.600 --> 00:22:55.280
but without having copied anything.

22:55.280 --> 22:57.760
And this one will disappear...

22:57.760 --> 23:00.240
this one as well-- or should hopefully,

23:00.240 --> 23:03.360
thanks to the `require`.

23:03.360 --> 23:09.840
Here we have a `hash` missing,

23:09.840 --> 00:23:11.840
and we have some functions

00:23:11.840 --> 00:23:14.000
which are unknown,

23:14.000 --> 00:23:14.666
so let's see... 

00:23:14.666 --> 00:23:18.240
Where is this function defined?

23:18.240 --> 23:21.679
Nowhere.  Huh, wonderful, okay.

23:21.679 --> 00:23:25.200
So we'll just leave it like it is, 

00:23:25.200 --> 00:23:27.120
and that's going to be 

00:23:27.120 --> 00:23:31.360
for the author of the package to fix.

23:31.360 --> 23:37.120
How about this one?

23:37.120 --> 23:40.240
Oh, okay, so it's defined in `enwc.el`

23:40.240 --> 00:23:41.679
so presumably, 

00:23:41.679 --> 00:23:44.559
this is going to disappear as well.

23:50.159 --> 23:51.030
One more...

23:56.159 --> 23:58.640
Okay, so this one

23:58.640 --> 23:59.919
is just like the previous one.

23:59.919 --> 24:04.000
We're going to leave it at that.

24:04.000 --> 24:06.720
And this is it!  Huh, wonderful.

24:06.720 --> 24:10.000
So let's recompile.

24:16.080 --> 24:23.520
Oh, we have a warning for `fin`.

24:25.679 --> 00:24:28.640
This variable seems not to be used

00:24:28.640 --> 00:24:32.000
anywhere in the file, so we're just

24:32.000 --> 00:24:33.440
going to remove it.  

00:24:33.440 --> 00:24:34.880
I leave it there just in case 

00:24:34.880 --> 00:24:36.000
someone needs later on 

00:24:36.000 --> 00:24:37.679
to look for a `fin` variable 

00:24:37.679 --> 00:24:39.760
to see where it used to be.

24:39.760 --> 24:41.600
Again, you know, maybe it's actually used...

24:41.600 --> 24:43.519
yeah, dynamic scoping somehow,

24:43.519 --> 24:46.159
but given the short name,

24:46.159 --> 24:48.960
I presume this is not the case.

24:48.960 --> 24:51.200
Here, oh, that's the code removed

24:51.200 --> 24:52.559
that had a hash missing.

24:52.559 --> 24:54.159
That's the one that's not defined.

24:54.159 --> 24:56.799
This one is not defined,

24:56.799 --> 24:58.000
and this is it.

24:58.000 --> 25:03.039
Let's make a last recompilation

25:03.039 --> 25:06.080
to see if we missed yet something else.

25:06.080 --> 25:07.919
Nope, and that's it, okay.

25:07.919 --> 25:11.200
Well, here we go; we're done.

25:11.200 --> 00:25:14.240
Okay so this was it.  

00:25:14.240 --> 00:25:15.440
You've seen, I think,

25:15.440 --> 25:18.000
pretty much examples of all of those,

25:18.000 --> 25:20.159
and I hope you enjoyed it.

25:20.960 --> 25:22.580
Lessons to take home:

25:22.580 --> 25:23.919
use the byte compiler.

25:23.919 --> 25:26.000
You can also use `flymake-mode` instead.

25:26.000 --> 00:25:31.600
I recommend enabling it as much as you can,

25:31.600 --> 25:33.520
and head the warnings.

25:33.520 --> 25:35.440
Follow the warnings. Try to fix them.

25:35.440 --> 25:37.200
If you can fix all of the warnings,

25:37.200 --> 00:25:38.080
it's always much better, 

00:25:38.080 --> 00:25:39.200
because then the new warnings 

00:25:39.200 --> 00:25:40.960
really show up.

25:40.960 --> 25:42.880
And once you've done it, it's really

25:42.880 --> 00:25:44.559
kind of-- because there's always 

00:25:44.559 --> 00:25:46.799
new things coming up.

25:46.799 --> 25:48.799
And I think this is it.

25:48.799 --> 00:25:50.720
I hope you liked it, and thank you 

00:25:50.720 --> 00:25:56.000
for attending this presentation. Bye.

00:25:56.000 --> 00:25:57.000
[captions by Hannah Miller]