Eev and TikZ, or: how to learn TikZ using a REPL (subtitles)

The main page about this video is here.
Its index is here.
Its subtitles in Lua are here.
The rest of this page contains a conversion of the subtitles in Lua
to a slightly more readable format.

00:01 Hi! My name is Eduardo Ochs, I'm the author
00:04 of an Emacs package called eev, and the name of
00:08 this video is: "Eev and TikZ, or how to
00:11 learn TikZ using a REPL"... and this is a
00:13 picture of me in and a REPL - you can see that
00:16 I'm very happy because I have a REPL
00:18 with me.

00:20 This video complements what is in this
00:23 page here - so I'm going to use lots of
00:26 technical terms that are explained in
00:28 the web page and I'm not going to
00:30 explain them here.
00:36 First of all...
00:39 I tried to learn TikZ the first time
00:42 many years ago, in 2014, and I failed
00:48 miserably, many, many times. I've
00:51 tried it several times, and
00:54 every time I gave up with the
00:57 feeling that my brain was too small for
00:59 learning TikZ.
01:00 And about one month ago I finally found
01:03 a way that worked for me for
01:06 studying TikZ, and it used links to
01:10 the manual - I'm going to show them in
01:13 a minute -

01:15 I mean links to both the PDF of the
01:18 manual and to the source code of the
01:20 manual - a REPL that I can run from Emacs,
01:24 and a way to extract examples from the manual

01:29 Let me show a first example - here.
01:33 This link here -
01:36 I will have to use a smaller font - this
01:39 link here opens my file with notes about
01:42 TikZ. You can see that it's
01:47 very big... it has about 4000 lines at
01:50 this moment, and it's very messy.

01:52 This thing here is an index.
01:56 Some of the sections are good,
01:59 some of the sections are totally crap,
02:01 and whatever ... and this link here goes to
02:04 the section that I want to discuss.

02:09 So, this goes to this section here, about
02:12 horizontal and vertical lines...
02:16 and these first links here point to
02:19 the manual. If I open this one - note that
02:22 it ends with "page" here - it opens the
02:25 page of the manual in the usual sense... in
02:27 the sense that it opens a PDF.
02:29 It opens a PDF of the manual at this
02:32 page, and this is a comment that the
02:36 function
02:38 find-tikzmanpage ignores, so the
02:41 comment is just for humans.

02:44 So, if I execute this...
02:47 it takes a few seconds because the
02:49 the PDF is very big... and it opens the PDF
02:53 on page
02:54 152 and what I'm going to show is
02:58 something related to this example here.

03:02 So the manual explains that
03:05 sometimes we want to connect two points
03:07 via straight lines that are
03:09 only horizontal and vertical and for
03:11 that we can use this notation, -|,
03:13 and this one, |-...
03:16 and it gives this example here. So this
03:18 is the output of the example and this is
03:21 the source code of the example.
03:24 Let me go back/

03:25 If I execute this sexp here...
03:29 it will take several seconds to run
03:32 because it will have to run a
03:34 program called pdftotext to convert
03:38 the PDF to text, and the manual is huge...
03:41 it's about 1300 pages -
03:45 so it takes a while
03:47 and then it is going to go to the page
03:49 152 of the manual
03:52 converted to text - it finds that page by
03:55 counting formfeeds - and then it will
03:58 search for this string here
04:01 in the converted text.
04:11 Here -
04:13 So this is the the name of the command that
04:20 was run to generate the converted
04:23 version,
04:24 and if I do not delete this buffer then
04:27 going back to the manual is very quick. So
04:30 if I execute this again it goes back to
04:32 the manual immediately.

04:35 And note that
04:38 this corresponds to this section of the
04:41 manual here...
04:43 and the first obvious way to extract the
04:47 source code of these example here is to
04:50 simply take this text here,
04:57 copy this to my notes and edit this a
05:00 bit to delete everything from
05:04 this column to the left. And note that
05:07 there's an A and a B here these letters
05:10 are there because here in the manual in
05:13 the example we see an A and a B - here, in
05:16 the image.

05:20 Until a few weeks ago when I was
05:23 extracting examples from the manual I was
05:26 always
05:27 using these conversion to text here, and
05:31 I was editing these things by hand... but
05:35 then I realized that
05:36 maybe I should take a look at the
05:40 source code of the manual, that is a
05:42 huge .tex file,
05:46 and I could try to see how these
05:49 sections and these examples are coded in
05:51 the manual... and it turns out that it's
05:53 very easy to extract the examples from
05:55 the manual.

05:57 If I execute this sexp here - note
06:00 that the suffix is "file" -
06:03 this thing here opens a file with this
06:06 name in a certain directory and searches
06:08 for the first occurrence of this string
06:10 here...
06:12 and what we get
06:14 is this. Here is the one of the files
06:19 of the source code of the manual... here we
06:22 have a listing of everything in this
06:24 directory... so we have lots of files that
06:26 start with pgf-manual-blahblahblah
06:31 and we find a subsubsection with this
06:37 title here...

06:42 and here we have this block,
06:45 that starts with \begin{codeexample} and
06:48 ends with
06:49 \end{codeexample}, and this is exactly the
06:52 the source code that I want, so I realized
06:56 that in many cases it was much easier to
06:59 simply extract
07:00 this code here from the source code of
07:03 the manual and then try to run that code.
07:09 Anyway, let me go back again.

07:12 Remember that I said that I
07:15 found a way of testing the examples in
07:17 the manual using a REPL. This is a demo
07:20 of this this REPL... I'm going to explain
07:22 it in details very soon - now I just want
07:27 to demonstrate how it works.
07:35 if I execute these three lines here
07:38 then eepitch will create a target
07:41 buffer running Lua in the
07:44 right half of this frame it will let's
07:48 do that now. So now we have this...
07:50 And now if I execute this line here
07:54 it will make Lua load a certain file,
08:01 that is the REPL - no, the tricks with the
08:04 REPL that I'm going to explain soon... and
08:08 this thing here defines a drawing in TikZ.
08:13 And when I run this line here - show() - it
08:16 takes a few seconds because it produces
08:19 a .tex file, it saves the .tex file to disk...
08:22 this sexp here visits the .tex file...
08:26 it is just this. So: it has a
08:30 header, a footer, and this thing in the
08:32 middle.

08:36 And it said that, uh...
08:40 The class "Show" compiled the .tex file
08:46 and everything went well - "Success!!!".

08:51 And now I can run this thing here - note
08:53 that this is a red star line, so eepitch
08:59 interprets everything at the right of
09:01 the red star as Lisp, and executes that
09:04 as Lisp... and when I do that
09:07 it will show the PDF: here.
09:11 And the nice thing is that
09:18 I can make changes to this drawing. For
09:21 example, I can change the scale of the
09:24 drawing, and then I can recompile
09:26 everything and show the PDF again...
09:29 and you can see that the PDF is
09:33 always shown here, so it's very easy
09:35 to compare one version with another.
09:39 And by the way I can even
09:43 execute these lines here
09:45 in another order - for example,
09:49 I can execute this one, and then skip the
09:52 second one, and then run the show() and the
09:55 (tikz-show)...
10:01 So... I've just
10:03 changed a parameter in the drawing,
10:08 and I produced a new version and I showed
10:10 the PDF of the new version.
10:12 So this is the way that the REPL works.
10:15 There are several variants of this
10:18 function here that shows the PDF...
10:21 one of the variants is this one -
10:27 I can run (tikz-showtex)
10:33 here... the scale appears here inside of
10:38 the scalebox{...},
10:40 so if I change the scale to 1.5, and I
10:43 save the .tex again, and I run showtex()
10:46 again, this 2 here will change to
10:49 something else - it will change to 1.5.
10:53 Let's see. Pay attention - here -
10:59 ta-da! And now I'm going to show
11:03 how to run... no, how people can test this
11:07 by installing just four files, and
11:11 then I'm going to to show a series of
11:13 exercises that I have prepared for
11:16 people who want to take this more
11:18 seriously and who want to use this tool
11:21 to study TikZ by extracting examples
11:26 from the manual.
11:27 By the way, let me just explain one thing
11:30 that is very interesting and very weird
11:33 that will appear later, that is this line
11:36 here. This function, tiks, is an alias for
11:44 the function... find-tikzsearch-links?
11:48 Oops, I don't remember! Let me try...
11:53 "tiks", with an "s" at the end, is an
11:56 alias for find-tikzsearch-links.
11:59 And when I run this it produces a
12:02 temporary buffer with several sexps
12:04 that I can use for locating an
12:08 example in the manual... I mean, both in
12:11 the PDF of the manual and in the source
12:13 code of the manual...
12:15 and other related things that we are
12:18 going to see soon.
12:21 Let me stop this video... and part 2
12:29 starts in a few seconds.


;; Part 2

12:33 Hi! I'm back. This is the part 2 of the
12:35 video...
12:38 In the page about eev and TikZ
12:41 the section 4 is called "Trying it".
12:45 Let me show it here. Bigger font...
12:52 The instructions are here. We are
12:54 going to copy this thing to a buffer in
12:56 Emacs, but let me just make some comments
13:00 before doing that.
13:03 We are also going to execute a function
13:06 here that will show a certain script,
13:08 that contains tests that we will run...
13:14 The prerequisites are quite minimal - we
13:17 just have to have Emacs, eev, pdf-tools,
13:21 that is a package that is in MELPA,
13:23 Lua, and a TeX distribution with TikZ.
13:30 Let me show how these things work... but
13:33 before showing this let me go back to to
13:37 here and make some comments.
13:40 These red bullets here, they will
13:44 behave as red stars even if they
13:48 do not show in red.
13:50 This is explained here in the main
13:52 tutorial. It says that
13:55 it is possible to make other
13:58 characters play the role of
14:00 the red star, and by default the bullet
14:03 can play the role of the red star...
14:08 And we can run this thing here to make
14:11 the bullets appear in red, but I'm not
14:13 going to do that now. And the second
14:16 comment is that
14:19 lines that start with two red stars are
14:22 treated as comments, and are skipped.
14:26 So, let me copy this thing here to my Emacs -
14:30 sorry to a buffer... I'm running an
14:35 Emacs in a quite minimal setting,
14:39 in a temporary directory... sorry -
14:46 this is the home directory that I'm
14:48 using, so it's a fake home directory with
14:50 just a few things - I have just installed
14:52 PDF tools here...
14:55 and let me copy this script here. I will
14:59 have to use a smaller font...
15:04 note that these bullets do not appear in
15:06 red, but they are going to behave as red
15:09 stars, I promise.
15:11 So, f8 here, three times... creates
15:17 a target buffer running a shell...
15:21 then I'm going to run these things here,
15:23 and here we see four "wget"s...
15:33 and now I'm going to load this file here.
15:36 Note that it corresponds to this file
15:39 here.
15:42 It defines a few functions. One of these
15:44 functions is this one, that just displays
15:48 a temporary buffer.
15:49 Let me run it now.
15:55 It shows this temporary buffer here, with
15:58 the script with tests. We have
16:01 just run some code that corresponds to this
16:04 section here, the section 0 here,
16:07 called "Basic installation"... and now we
16:10 are going to run this thing here.
16:12 These lines start with two red stars,
16:15 so they're going to to be treated as
16:17 comets, and we are going to see here in
16:21 the echo area something that says:
16:22 "Comment: blah blah blah blah".
16:25 So let's do that now.
16:28 And now this line here is going to be
16:32 very important. Note that it
16:34 has a single red star, so it's not a
16:36 comment - it's going to be executed as
16:39 lisp and it sets a
16:45 an environment variable that says where
16:49 Lua should should read its init file
16:52 from.
16:54 If I remember correctly that
16:56 variable is not set now, so if execute
16:59 this thing here
17:01 Lua will complain that this function,
17:04 ee_dofile, is not defined.
17:06 So let me run this block again
17:11 When I run this line Emacs will
17:15 define this environment variable for all
17:18 children processes, and I'm going to
17:21 restart the Lua interpreter...
17:24 Here - and now it's going
17:27 to use this
17:28 environment variable here, so now this
17:31 line will work - it will load this
17:35 Lua file here.
17:37 We can also execute this with M-e to
17:41 take a look at this file.
17:43 By the way, it says
17:46 "find-angg not configured"...
17:49 Let me cheat a bit. Let me run one thing
17:53 here without explaining it.
17:59 I'm going to explain this in one of the
18:01 exercises, I promise!
18:05 If I run this thing now,
18:09 then it accesses that file by using wget -
18:13 I mean it downloads a copy of that file
18:16 without saving it to disk...
18:19 and I do not have lua-mode installed
18:22 in this minimal setting here,
18:28 so the colors are a bit boring...
18:33 but anyway, we can access this Lua file
18:36 here, and now let's run this test. This
18:39 test is a bit simpler than the test that
18:41 I've shown before.
18:44 I'm going to run these four lines here,
18:47 and note that this thing has a "tikz"
18:49 here...
18:51 if I just executed this
18:55 then the value of tikzbody would be
18:58 just this string here, that
19:00 is between these funny delimiters -
19:02 between this "[=["
19:05 and this "]=]"...
19:06 but we had a "tikz" here, and this says
19:11 that we have to run the function "tikz"
19:14 with this argument, and the function
19:16 takes this this argument here and
19:19 treats this thing here as something that
19:22 has to be expanded... so every time that we
19:25 expand this string here, this thing here
19:29 between double angle brackets will
19:31 be replaced by the result of evaluating
19:35 it, and also this thing here,
19:39 and also this thing here...
19:44 In the beginning this variable is nil,
19:47 this variable is also nil,
19:50 and
19:53 the function that that evaluates these
19:56 things between double angle brackets
19:59 treats
20:00 things that evaluate to nil as empty
20:04 strings, so this thing here is going to
20:06 become an empty string,
20:08 also this one here,
20:10 but in this one here something
20:12 different is going to happen -
20:14 the variable gridsize is nil, but we
20:19 have this "or" here, so this thing is nil
20:22 and the result of this bigger expression
20:24 is going to be this string here. So
20:30 the result of
20:33 evaluating this part here is going to be
20:35 this string here.
20:38 I have just
20:41 sent this thing without the
20:44 "tikz" - let me run this thing again with
20:47 the "tikz"...
20:48 and now let me run the show() that will
20:51 save this thing into a .tex file... I mean,
20:53 it will produce a .tex file... it will save
20:55 the .tex file, and it will try to compile
20:58 the .tex file to generate a PDF.
21:03 Ta-daaa: "Success!!!"
21:06 Now I can run this thing here -
21:09 remember that it starts with a red
21:11 star, so Emacs is going to execute to this
21:13 thing...
21:17 ah, one second... let me
21:25 try this again - sorry...
21:30 I forgot that I'm in a very minimal
21:33 environment, so it
21:36 wasn't searching for pdf-tools in the
21:38 right place...
21:39 Anyway. Note that I have executed
21:43 this thing, that is a function... it's a
21:47 relatively low level function - it just
21:49 splits the frame into two windows, and it
21:52 shows a PDF in the window at the right.
21:56 We are going to see something much
21:58 better in in a few minutes.
22:01 Now I'm going to run this lines here
22:04 these two lines are sent to the Lua
22:06 REPL...
22:08 this line also, but this one takes a few
22:11 seconds to run, and it shows all
22:13 these messages here...
22:15 and now I'm going to run this line - the
22:19 (find-pdftoolsr-page ...) -
22:24 and it shows a changed version in which
22:28 gridoptions now...
22:31 I mean, this thing here, now when it
22:36 is expanded it becomes this string here...
22:40 so the grid appears in a lighter color.
22:43 And now I'm going to run this block here
22:47 and this is going to change the value
22:50 of the variable gridsize.
22:53 Remember that gridsize appears here...
22:57 so when I change this this variable,
23:01 gridsize, to this string,
23:05 the result of evaluating this expression
23:07 here is no longer going to be the thing
23:10 at the right of the "or" - I mean this
23:13 string here... it's going to be
23:16 this other string.
23:18 So TikZ is going to use a smaller grid.
23:21 Here we have a grid
23:26 whose width is six units and whose height
23:30 is four units... we are
23:34 going to change that to four units and
23:37 three units. Let's do that now.
23:40 "show()" takes a few seconds to run because
23:42 it produces a PDF... and now let's show the
23:45 result... ta-daaa: smaller grid!
23:49 And here is another part of the demo.
23:54 instead of displaying the PDF I'm going
23:58 to use the function savetex(),
24:00 that just produces .tex, but
24:03 does not generate a PDF from it, and this
24:07 function here, that displays the .tex file
24:10 at the right side.
24:12 Let's see. Note that this first line
24:16 sets gridoptions and gridsize to nil
24:19 and nil again, so we are back in
24:22 the initial situation...
24:24 savetex() just says
24:28 "Saved the .tex file in blah blah blah"...
24:31 and now I'm going to run this thing here,
24:34 that produces a
24:37 a window setting with three windows,
24:41 and it shows the .tex file here at the
24:43 bottom.
24:46 And now I'm going to run this other
24:48 block here...
24:52 note that I'm changing the gridoptions,
24:55 and gridoptions appears here, after the
24:59 first \draw, so pay attention to what
25:02 happens here in the .tex file
25:05 we're going to see that here
25:09 appears a thing between square
25:12 brackets that says
25:18 "[color=gray!20]".
25:20 So pay attention... here...
25:24 savetex(), and now (tikz-showtex).
25:31 And now something similar, but the grid
25:33 is going to change to (4,3).
25:37 Pay attention here...
25:43 So (tikz-showtex) is a low-level
25:46 function that we can use to
25:48 inspect what happens with .tex file...
25:53 And now I'm going to
25:57 show the the function that we're going
25:58 to use most, that is the function that
26:00 instead of showing the .tex file - here -
26:03 its shows the PDF file here.
26:06 So, same thing. Let's reset gridoptions
26:09 and gridsize to the initial state,
26:12 show()
26:13 and (tikz-show). So this is our initial
26:16 drawing -
26:17 the grid appears in black.
26:20 Now let's change the color of
26:23 the grid, and run show() again, and run
26:27 (tikz-show)... and now it's going to to show
26:30 the changed version of the PDF, in which the
26:32 grid appears in light gray.
26:35 And now let's change the size of the
26:38 grid. The grid is currently 6 units by
26:41 4 units, it's going to change to 4
26:45 units by 3 units...
26:50 that's it - you can see that the rectangle
26:52 is smaller.
26:55 So, this is the the basic test that
26:59 you can run with without installing
27:01 anything... I mean, you just need these
27:04 prerequisites here...
27:08 Emacs, eev, pdf-tools, Lua 5.1, and a TeX
27:11 distribution with TikZ...
27:15 and by the way this thing puts four
27:19 files in this directory, that is hard
27:21 coded at the moment... and it creates some
27:24 temporary files in /tmp/.
27:35 So, now suppose that you are interested
27:41 in trying this more. Then my suggestion is:
27:46 copy these things here - these lines here -
27:48 to your init file.
27:52 Some people use init files with other
27:54 names, but I prefer to call them by the
27:57 the old name which is ~/.emacs...
28:03 but this is an abuse of language - I mean,
28:06 for some people theirs init file is going
28:08 to be ~/init.el, or
28:14 ~/.emacs.d/ something, whatever...
28:20 So let's copy these things here to my
28:23 init file...
28:32 and now every time that we start Emacs
28:36 it is going to set
28:40 the init file for Lua to this file here,
28:43 as I've shown before, and it's going to
28:46 to load
28:50 the file that defines this script that
28:53 we're using, and blah blah...
28:57 um sorry sorry
29:02 and if you want to deactivate these
29:05 things you just need to comment out
29:08 to this region either in this way, or in
29:12 this way here...
29:17 oops, sorry,
29:23 let me do this by hand... sorry, one of my
29:26 favorite Keys is not defined.
29:29 so, that's it. This thing was commented
29:32 out.
29:34 But right now I do not want it to
29:36 comment it out - I want to use it.
29:40 Note that
29:44 this thing starts with three comments,
29:47 here... I use this a lot in eev - instead
29:51 of using customize I use
29:57 "setq"s, and "defalias"es, and
30:00 "defuns", and whatever else... and there is
30:03 a section here that has links that
30:05 explain why I prefer to use alternatives
30:08 to customize - low-level alternatives -
30:11 instead of using customize itself.
30:15 And one trick that I always use is
30:18 that every time that I put a block of
30:20 code in ~/.emacs
30:26 I start with the line that says "From:"
30:30 that gives me more information about
30:33 what these lines do, and where you can
30:36 go to understand more about them.
30:39 So, if I execute this...
30:41 it will open this .el file..
30:45 and note that here we have the
30:47 definition of find-tikz1-links...
30:52 and it is basically just a big
30:55 template that displays this thing in a
30:57 temporary buffer.
31:00 And it also has a link that goes to a
31:04 certain anchor in this file...
31:08 that anchor points to the place in which
31:12 I define the function "tik", without a
31:15 "z" at the end...
31:16 and it inserts an eepitch block that "runs
31:21 tikz1.lua". Let me show how to
31:23 use this.
31:27 Let me go back to here - this is just a
31:30 random scratch buffer... if I run
31:34 M-x tik here
31:37 it inserts this block... let me show
31:41 this again...
31:43 it inserts this block, and this is
31:45 something that I can modify. I can put
31:48 this block in any place, and if I run
31:50 this thing here it creates Lua
31:53 buffer...
31:55 I mean, a target buffer for eepitch
31:59 running Lua.
32:00 Now this first line loads
32:04 tikz1.lua, that defines "tikz"
32:07 and "show"...
32:12 and here it has a very short demo of a
32:16 drawing.
32:18 The idea is that this is just a
32:20 placeholder that you can replace by
32:22 something else...
32:23 it's to remind people that you can
32:26 put text code inside this thing here.
32:30 Now let me run the show()
32:34 and the (tikz-show)... and this thing drew
32:38 an orange triangle.
32:41 I can, for example,
32:43 replace this by "red"...
32:47 and run this again,
32:50 and now my triangle is red.
32:56 Let me stop this part of the video here.
33:00 In the other part I'm going to
33:01 explain these things here...
33:14 we have just done the "Not so basic
33:18 installation", that lets people explore
33:21 TikZ with just a few
33:24 settings, and now I'm going to explain
33:27 the exercises that
33:30 people can use to learn how to extract
33:33 examples from the TikZ manual.
33:36 So part 3 starts in a few seconds.

;; Part 3

33:40 Hi! this is the part 3 of
33:43 the video,
33:45 that is only for the people who are
33:47 asking: how can I write things like this,
33:52 like this block that we saw in the first
33:54 part, myself?
33:56 And note that right now, in this minimal
33:59 setting in which I'm running this Emacs
34:04 here, in a fake home directory, I do not
34:07 have a copy of the
34:10 TikZ manual, I do not have a
34:14 copy of the source of the TikZ manual... so
34:17 many of these things are not going to
34:19 work. If I execute this thing here it says
34:22 that this function is not even defined...
34:25 this function is not defined also... this
34:28 function is not defined... so it's not even
34:31 in a state in which it searches for the
34:35 manual and for the source of the menu in
34:37 the right places.
34:44 What we are going to see is what is in
34:46 the
34:48 third section here... the section 3 here,
34:50 because it has a 0th section.
34:55 We just saw the sections 0, 1, and 2,
35:00 and we are going to see this one now.
35:02 Let me just return and execute this.
35:05 Here we are.
35:08 I say that these exercises are
35:11 explained in this section of the page
35:13 about eev and TikZ, but at this moment
35:15 this section does does not exist... but it
35:18 will exist very soon.
35:20 And there is also another similar
35:23 function, similar to find-tikz1-links,
35:26 that has some spoilers... at this
35:28 moment it has very few spoilers but I'm
35:31 going to add more spoilers soon.
35:34 This section has lots of exercises
35:38 and in
35:42 this video I'm going to show very
35:43 quickly how to do these exercises, and my
35:45 recommendation is: watch this
35:48 video with subtitles and with the trick
35:51 that eev uses to point to positions in
35:54 a video,
35:56 to follow the instructions in
36:00 each of the exercises step by step.
36:03 All the exercises are going to be
36:06 of the same type which is just
36:09 reproduce yourself the steps that I'm
36:12 performing in this video... so they do not
36:15 require a lot of creativity, I mean, sorry,
36:18 they do not require any creativity, they
36:21 just require people to familiarize
36:23 themselves with some functions that I
36:26 use in eev.
36:27 And let me make a very important comment
36:30 which is that most of the functions that
36:34 we are going to see now, they look like
36:36 5-minute hacks... my presentation at the
36:40 EmacsConf2020 was exactly about that, about
36:44 some design choices in eev,
36:47 and its title was exactly "On why most of
36:51 the best features in
36:54 eev look like 5-minute hacks".
36:58 But let's go back, and let me show
37:04 how to do the exercises.

;; a) [tik]

37:09 We just saw how to do this exercise here,
37:12 but this exercise (a) here, whose name is
37:16 "[tik]"...
37:17 it asks us to use M-x tik to
37:22 create
37:23 an eepitch block that compiles and
37:26 displays a drawing whose body is this.
37:30 So I'll have to copy this file to my
37:35 notes... let me go to my notes - here -
37:37 remember that when I type
37:42 when I type M-1 M-j this opens
37:46 the file with my notes, that is ~/TODO...
37:49 so I'm going to put all my
37:53 notes about these exercises in this file
37:56 here,
37:58 which is the file that I recommend
38:00 people to use to to put all their messy
38:04 things there.
38:09 Let me yank these lines here,
38:16 let me change the indentation... and if
38:19 I run M-x tik it creates a block like
38:24 this, but the exercise asks us to change
38:27 the body to this other body here.
38:32 Now let's run this thing here... I will use
38:36 a smaller font -
38:44 it created the PDF successfully. Let's
38:48 show the PDF. Ta-da - we have a grid with
38:52 this size four units in the horizontal
38:56 direction, and three units in
38:58 the vertical direction, and
39:02 this second draw here has drawn a red
39:07 triangle here.
39:09 So this was the first exercise.
39:12 Let me just put some notes here.
39:20 Now let me go back to the to the
39:23 exercises.

;; b) [.emacs-1]

39:25 The second exercise is this one.
39:33 Let me copy it to my notes.
39:41 Actually we have already done that...
39:45 it says: copy the lines from the
39:49 section 2 to your init
39:52 file, restart Emacs, and check that this
39:55 thing here works.
39:57 Let me try.
39:59 Hm, these lines are already there...
40:12 I'm not going to restart Emacs because I
40:15 I've started Emacs with some command
40:19 line options to make it use certain
40:21 colors, and it would take me many seconds
40:24 to remember how to do that...
40:27 Anyway, so let me pretend that we did the
40:33 exercise b.

;; c) [.emacs-2]

40:35 Now let's go to the exercise c,
40:40 which is this one...
40:48 I have already fixed that but I did
40:50 not explain how. The thing is that by
40:53 default when we run find-es something
40:57 Emacs says that find-es something is
41:02 not configured.
41:04 In this case... sorry -
41:10 let me see what happens here...
41:23 so this thing is configured. The
41:27 instructions say that we have to
41:30 execute this thing here. Let me just
41:32 explain how this thing works. If I type
41:35 M-x and I run this function here -
41:37 find-angg-es-links -
41:42 it shows a way to configure find-es and
41:46 find-angg... it explains how they
41:49 work on my machine and how people
41:52 can also use it...
41:53 I mean, when I run find-es and find-angg
41:56 in my machine they open local files
42:00 that have my scripts, my
42:03 programs my notes and so on. Other people
42:06 can also access my scripts if they
42:09 redefine these functions in a certain
42:11 way
42:12 to make them use wget, and there's a
42:16 video here that explains how how this
42:18 thing works. So if people
42:20 want to understand
42:23 what this thing does the recommendation
42:25 is: watch these videos here. If I remember
42:28 correctly they just need to
42:32 watch 30 seconds starting from this
42:35 point and another 30 seconds
42:37 starting from this point.
42:39 So let's let me pretend that this
42:42 exercise is done,
42:44 and let me go back to the list of
42:47 exercises.

;; d) [manual-pdf]

42:50 Exercise d.
42:57 Remember that I said that we don't have
42:59 a copy of the of the manual yet...
43:07 to download a copy of that manual
43:12 in PDF we have to run M-x brep.
43:17 If we run this here
43:20 it asks for a URL, and then it opens this
43:25 temporary buffer here with this script.
43:29 If people want to understand what this
43:31 thing does they can go to the source
43:34 code by running this line here,
43:39 and then the comments in the source code
43:43 have pointers to the manual,
43:46 to the place that explains how these
43:49 things work...
43:54 and the manual also has some links to
43:57 videos, if I remember correctly...
44:03 oops, sorry, this this tutorial does not
44:07 have links to videos, but it is quite
44:09 clear.
44:15 Anyway,
44:16 to download the local copy we have to
44:19 run M-x brep here, and it displays this
44:24 temporary buffer and what we have to do
44:26 is that we have to execute these
44:39 commands here, but it says that...
44:42 in my previous test I had already
44:45 downloaded a copy of the manual so it's
44:47 already there. And we can also use these
44:50 lines here to test if the file was
44:54 downloaded. It was -
44:57 and the
45:01 othe part of this exercise says
45:04 that we have to produce a pair made of a
45:07 code-pdf-page and a code-pdf-text that
45:10 makes these links work. This is also
45:12 explained in the tutorial. In the page
45:15 about the eev and TikZ I'm going to give
45:17 links to the sections of the
45:20 tutorial that explain everything... but let
45:22 me show very quickly how we can do that.
45:27 When we ran brep here one of the sexps
45:31 that it produced was this one...
45:38 now I'm in dired mode, and here I
45:43 can type M-h M-e... it creates a
45:47 temporary buffer like this,
45:49 and what exercise asks is... that
45:59 we create links like this that work.
46:02 So the "{c}" that we have to put here
46:06 is "tikzman".
46:11 I have edited this first line here, to
46:16 change the value of
46:20 of "{c}", and if I run this
46:24 line again it will regenerate this
46:27 temporary buffer from a template and all
46:30 these "{c}"s are going to be replaced by
46:32 this new value here - "tikzman".
46:35 And now we have this block of
46:38 links that point to a certain PDF file...
46:43 and what the exercise asks is that we
46:46 produce these code-pdf-page and this
46:49 code-pdf-text if I execute them...
46:53 let me execute them. The first one defines
46:55 this function here, find-tikzmanpage,
46:58 the second one defines this function here...
47:02 remember that if you need more
47:05 information about what they do you can
47:07 just add a "find-" here in the beginning
47:10 and then
47:11 execute this new sexp and then it will
47:15 have some explanations, a link to the
47:17 tutorials, and so on...
47:20 but now they have defined these things
47:23 and this sexps should work. This one
47:27 should open the manual in
47:29 PDF - this is the first page of the manual
47:33 in PDF -
47:34 and this sexp here is going to take
47:37 many seconds because the manual is huge...
47:40 and it's going to open the the manual
47:44 converted to text.
47:46 So a bit of patience please...
47:52 a bit more please...
47:55 oh no, it takes ages!...
47:58 Here we are.
48:02 this thing worked correctly it ran
48:05 pdftotext to convert the manual to text,
48:08 and at some point we're going to use
48:10 this thing to
48:14 point to titles of sections, sometimes
48:17 we're going to use this to copy and
48:19 paste examples, and so on...
48:22 so the answer to this exercise is these
48:28 two "code-pdf-*"s -
48:30 these two "code-*" lines. And these two
48:34 lines here are tests.

;; e) [manual-git]

48:37 Let me go back to the exercises. Now
48:41 I'm going to show how to do the
48:44 exercise e.
48:48 The exercise e says that we have to
48:52 start from this URL here, that points to
48:55 a git repository, and
48:59 we have to use this to download the
49:02 source code of the manual... and we
49:04 have to define these three...
49:08 we have to make these things
49:11 work using `code-c-d's.
49:14 And here people will have to consult the
49:20 spoilers because it's not clear what
49:23 this directory means... I mean, to what
49:27 directory this thing has to
49:29 point, and to what directory this thing has
49:31 to point, whatever...
49:32 Anyway. I can type `M-h g',
49:42 and it runs a function called
49:46 find-git-links...
49:48 and now I can run this script here
49:51 and it clones the git...
49:53 oh no -
50:02 It used the wrong directory.
50:08 Let me fix that. Sorry.
50:13 So now the cd worked...
50:20 it's downloading - I mean, it's cloning the
50:23 git repository...
50:35 and if I want I can inspect the git
50:39 repository using these links here -
50:43 but I do not want to do that now.
50:48 What I want to do is that I want to
50:53 create something like this,
50:56 but with a different name... I want to use
50:58 something different instead of "pgf" here.
51:01 So let me copy these two lines
51:05 to my notes...
51:07 what I'm going to do here is that I'm
51:09 going to replace "pgf" by "tikzgit"...
51:19 TikZ is actually PGF/TikZ, but
51:25 the name PGF is not used so much, so I
51:28 preferred to use the name "TikZ" almost
51:31 everywhere.
51:33 So this thing here defined
51:35 this function - code-tikzfile -
51:37 and several other functions...
51:40 remember that you can inspect
51:42 what this code-c-d does
51:44 running a sexp like this...
51:49 it defines this variable, ee-tikzgitdir,
51:52 and lots of functions with "tikzgit" in
51:55 their names... and if people need more
51:59 information about how this works
52:01 they can use these things here to go
52:05 to the tutorial.
52:11 So if I run this then I define
52:15 find-tikzgitfile, find-tikzgitgrep, and
52:17 other links like this, and this one opens
52:21 the source code of the manual...
52:24 and I also need some variants
52:30 of this... let me open the spoilers.
52:41 Here. What I really want is these three
52:47 `code-c-d's here...
52:51 and this one is obvious - it goes to the
52:58 copy of the git repository... this
53:01 one goes to the
53:05 directory where the source code of git
53:08 itself is - I mean, when you use
53:12 \usepackage{tikz} in your .tex file
53:16 it load files that were
53:18 originally here, but that were then copied
53:21 to the texlive distribution... sorry, to
53:25 tex texlive directories.
53:28 And this one is going to be very useful
53:32 and very used...
53:33 that is the source code of the manual
53:36 of TikZ.
53:42 Here we have
53:45 all the sections, and
53:48 chapters, and subsections, and whatever,
53:50 of the manual
53:51 in .tex files. We're going to use that
53:54 soon.
53:57 So, now...
53:58 well, the exercise e said that we had
54:02 to produce these three `code-c-d's
54:06 that make these sexps work...
54:07 and now they do work. This
54:12 one opens the copy of
54:14 the git repository, this one goes to
54:17 the source code of TikZ itself and
54:20 this one opens the source code of the
54:22 manual.
54:25 So now let me go back to the
54:27 exercises again...
54:31 we have just done this exercise here...

;; f) [.emacs-3]

54:34 Let me copy these two exercises to my
54:41 notes at the same time...
54:47 This exercise here asks people to
54:52 put more things in their init file.
54:57 It asks people to copy these
55:01 things to their init file, and it
55:03 recommends using the spoilers.
55:05 And the idea is that we are going to
55:08 copy this thing here to the init file...
55:11 and remember that if we type M-5 M-5 M-j
55:20 then we open the init file.
55:26 So let me copy this to the init file...
55:30 and note that
55:31 it has a "From:" line here, and the line
55:35 with the "From:" can be used to...
55:40 I mean, I forget things all the time, and
55:43 so I use these things to go back to the
55:46 places where the functions were defined,
55:48 where I found the instructions, and so on.
55:50 If execute this thing I go to the
55:54 temporary buffer with spoilers, and I see
55:59 this block here... that is where
56:02 this thing here came from.

;; g) [page]

56:10 Now the exercise g, called "[page]"...
56:16 it asks us to create links to a certain
56:19 page in the manual.
56:22 If I execute this thing it goes to the
56:25 conversion of the manual to text,
56:30 and the exercise says that we have to
56:34 produce a pair like this,
56:36 that points to that page...
56:39 and what we have to do is that we have
56:41 to go here, then we have to mark this
56:44 string and copy it to the key ring, and
56:47 then we have to type `M-h M-p'...
56:51 and then this is the pair
56:54 that we want.
56:57 This first link here opens the PDF of
57:00 the manual at that page...
57:07 those coordinates appear here, in
57:10 the middle of the
57:12 the instructions for drawing this
57:14 envelope here...
57:17 and now this thing here has a number
57:21 here saying to this function that it has
57:24 to count the form feeds to go to page
57:27 30 in the conversion, and then it has to
57:30 search for this string in the
57:32 manual converted to text. If I execute
57:35 this
57:36 it goes exactly to this page
57:39 but it also has this indication that we
57:42 have we are in page 30.

;; h) [src]

57:49 Next exercise: "h) [src]".
57:58 In this exercise we have to
58:01 to learn how to create a link to the
58:04 source code of the manual...
58:06 and we are also going to have to learn
58:09 how to use this - `tiks'. This is a 5-minute
58:12 hack, in the sense that I've mentioned
58:15 earlier and that is explained... I mean, the
58:19 design decisions behind these
58:22 5-minute hacks were explained
58:26 in my talk at the EmacsConf 2020.
58:30 If we execute this it creates a
58:33 temporary buffer with lots of hyperlinks,
58:37 and the idea is that we have to understand
58:42 what these hyperlinks do...
58:48 and we have to produce a hyperlink like this,
58:53 that points to a certain section of the
58:57 source code of the manual.
59:01 note that we don't have links like that
59:04 here... but we will have to use the grep
59:14 here to grep
59:16 in the directory that has this shorthand...
59:26 it found one occurrence of this
59:29 string, in this file here... so what I have
59:33 to do is that I have to visit this file...
59:35 if I type enter here it will go
59:38 to the line 271...
59:42 then I'll have to copy this thing to the
59:49 kill ring... and now the best way to create
59:52 a link to this string is to use...
59:55 I mean, the traditional way is by typing
59:58 `M-h M-h', here and then editing...
1:00:03 duplicating this line, editing this line
1:00:06 to add this string here, and so on... but
1:00:09 one of the things that I'm going to
1:00:10 present in the EmacsConf
1:00:13 is a very fast way to create
1:00:16 links like this.
1:00:17 So if this thing here is in the region -
1:00:24 in this case the region is not active,
1:00:28 but it is there -
1:00:31 and I type `M-x klfs'
1:00:35 this kills a link to a file and
1:00:41 a string in that file...
1:00:44 so if run this -
1:00:46 Gaaah! God! =(
1:00:53 Oh no, this is not loaded by default...
1:00:58 Let's see if I...
1:01:01 I'll have to to fix this later,
1:01:06 but let me
1:01:08 fix this by hand, sorry...
1:01:20 Let me see if this works now...
1:01:25 Ah, yeah! Sorry!
1:01:31 Let me do some mysterious things right
1:01:34 now...
1:01:41 I have use these aliases here.
1:01:44 Let me put these aliases in my...
1:01:50 Let me copy these aliases to the init file
1:02:04 and execute them...
1:02:07 so now this thing should work...
1:02:11 if I
1:02:13 mark the region here and I type `M-x klfs'
1:02:17 this should put in the kill ring a
1:02:21 link to this file and to this string in
1:02:24 this file.
1:02:25 Oops - let me run this again...
1:02:29 The message in the echo area says that
1:02:32 this has killed this sexp here...
1:02:36 and let me go back to my notes...
1:02:41 this is the link that the
1:02:44 exercise asks for.
1:02:46 If I execute this link I go to this file
1:02:51 and the source of the manual, and it
1:02:53 searches for the first occurrence of
1:02:55 this string there.
1:03:01 Next exercise...

;; i) [tiks]

1:03:10 "i) [tiks]".
1:03:15 Let me go back to my notes...
1:03:19 it says: start from this
1:03:21 hyperlink and make sure you know how to
1:03:24 use all the hyperlinks in the temporary
1:03:26 buffer that this function here, `tiks', has
1:03:29 generated.
1:03:34 This first line here just regenerates
1:03:37 the buffer in the sense that if I make a
1:03:39 big mess here I can just execute this
1:03:42 individual reconstruct the buffer in the
1:03:45 original way. This second line uses
1:03:50 a synonym for `tiks'...
1:03:54 this third line here goes to
1:03:57 the definition of this function -
1:04:03 it is here, and after the definition we
1:04:05 have a defalias,
1:04:08 so the two functions are equivalent.
1:04:16 This thing here is going to use wget to
1:04:19 access one of the files in my home site.
1:04:28 It has some notes about TikZ, and here
1:04:31 is an index that I have prepared
1:04:35 for the chapters of the manual - but this
1:04:38 index supposes that we are using an
1:04:40 older version - long story -
1:04:43 so the pagination is not correct...
1:04:45 for example, probably this thing
1:04:49 here is not going to point...
1:04:52 no, this one works but
1:04:56 let me see what happens here...
1:05:00 this one is four or five pages behind.
1:05:09 The right value here should be
1:05:12 something like this...
1:05:15 Almost!
1:05:21 Anyway, this is an index for
1:05:25 the chapters in the TikZ manual,
1:05:28 that is not going to work for you
1:05:30 because...
1:05:31 well, in the other exercises
1:05:35 I recommended to download the current
1:05:37 version of the manual...
1:05:39 and note that
1:05:42 this thing was downloaded by wget, so
1:05:45 it's in a temporary buffer...
1:05:57 in this case this
1:06:00 link is not going to work very
1:06:02 well because
1:06:04 this thing is not the name of a
1:06:07 chapter, it is the name of a subsection...
1:06:09 but whatever... this link here
1:06:14 is more like a button than like a link -
1:06:16 it puts this string in the kill ring.
1:06:26 We are going to see soon how to use that.
1:06:30 This thing here opens the the manual in PDF
1:06:36 in its page 3, where it has the table
1:06:39 of contents...
1:06:42 this one here opens the page 3 using
1:06:46 the conversion to text and now we can
1:06:49 use this thing here that I
1:06:51 have just pushed into the the top of the
1:06:54 kill ring to search for a certain string
1:06:57 if I go here and I type C-s
1:07:00 I enter the mode that performs
1:07:05 interactive search... if I type M-y here
1:07:09 it puts
1:07:12 the top of the kill ring here and I can
1:07:15 use that to find this section
1:07:18 in the manual.
1:07:19 And now I can search for other
1:07:22 occurrences here... because probably
1:07:24 I do not know a link to this page.
1:07:26 No, sorry, let me change the exercise
1:07:29 a bit. I will use this string here
1:07:38 to create a link to the index...
1:07:48 so this thing here is section
1:07:52 14.2.2 that appears
1:07:56 here, in very small letters...
1:08:06 and after doing that I can also
1:08:11 search for this other string here...
1:08:18 and use M-h M-p again to produce
1:08:22 a pair of links that go to the
1:08:26 real section in the manual.
1:08:29 So this goes to this section - here -
1:08:38 and this goes to this section converted
1:08:41 to text.
1:08:44 Let's go back. I was explaining
1:08:48 the lines in this temporary buffer here...
1:08:50 and this one was a bit mysterious, but
1:08:53 I have just explained how to use it.
1:08:58 These lines here...
1:09:01 in theory they go
1:09:06 to the index of the the manual, at the
1:09:09 very end...
1:09:10 and remember that you can
1:09:12 execute this to go to the source code
1:09:16 of that function,
1:09:19 and we can use that to change that to
1:09:21 the right numbers...
1:09:23 this is a bit advanced, but let me
1:09:26 explain it anyway.
1:09:30 The index is a few pages ahead of that...
1:09:33 that number. Let me see how many...
1:09:37 oh, no! Many pages. So, in this version
1:09:41 of the manual the index
1:09:43 starts at the page 1271
1:09:49 instead of 1235,
1:09:51 and I can go to the source code of
1:09:55 this function, and I can change this to
1:09:58 1271...
1:10:02 and then I can redefine this function,
1:10:08 and then I can use this to regenerate
1:10:10 this buffer, and now it has now it has
1:10:15 the right links to the index.
1:10:21 So this first link here goes to the
1:10:25 beginning of the index, but it
1:10:27 ignores this string...
1:10:30 and this other link here goes to the
1:10:32 beginning of the index and then it
1:10:34 searches for the string. I guess that
1:10:36 that is not going to work -
1:10:38 it says "Search failed", but whatever -
1:10:43 for other strings this would
1:10:46 work very well. For example,
1:10:56 if I wanted this...
1:11:03 then I could just use this thing here to
1:11:05 create
1:11:10 a link to where a certain string appears
1:11:13 in the index.
1:11:18 Well, as I've said in the beginning
1:11:21 this is a 5-minute hack with many
1:11:23 small hacks inside... and I've just
1:11:26 explained how we can fix the index, and
1:11:29 how we can create
1:11:30 links to an entry in the index.
1:11:36 These three lines are easier. We just saw
1:11:39 what they do. This goes to the
1:11:42 to the copy of the git repository,
1:11:46 this one goes to the
1:11:49 to the source of the manual, and this
1:11:52 goes to the source code of TikZ and
1:11:59 PGF themselves.
1:12:02 We can use this
1:12:04 three grep links here to search
1:12:12 the whole copy of the git
1:12:14 repository, or to... sorry, to search just
1:12:19 the source of the manual, or to search just
1:12:21 the source of TikZ and PGF.
1:12:27 And note that
1:12:30 I've used the an uppercase R here to to
1:12:34 specify that this grep has to be
1:12:37 recursive.
1:12:40 This one finds one occurrence,
1:12:47 this one also...
1:12:54 and this does not appears in the
1:12:57 source code of TikZ, I mean...
1:12:59 when people run \usepackage{tikz} then
1:13:05 this loads lots of packages and this
1:13:09 string does not
1:13:11 does not appear among the these packages -
1:13:14 these .tex files and the style files
1:13:17 that are loaded by \usepackage{tikz}.
1:13:23 And we can also use these URLs here
1:13:26 to go to the... oops -
1:13:30 I do not want to do that now, sorry... I'm
1:13:33 in the fake home directory... but we can
1:13:37 use this to to open the git repository
1:13:40 using a browser
1:13:44 So these are the explanations
1:13:47 for all the lines that appear in the
1:13:52 "make sure that you know how to use all
1:13:55 the hyperlinks"... there are many, and
1:13:57 some are quite technical. I have
1:13:59 just explained all of them.
1:14:01 So this was exercise (i).

;; j) [section]

1:14:07 Let's go to exercise (j).
1:14:17 Exercise (j) says
1:14:25 that we should start by this
1:14:27 hyperlink here, and
1:14:30 we have to use this to produce links to
1:14:33 a section of the manual. So this is
1:14:35 similar to what I did here,
1:14:37 but here I produced links to a section
1:14:40 called "Horizontal and Vertical Lines",
1:14:43 that was actually a subsubsection,
1:14:46 or a subsection, whatever...
1:14:50 And let me show how how we can do this.
1:14:57 My favorite way of doing this is by
1:14:59 using this to put the string
1:15:03 in the kill ring, then I go to the
1:15:05 table of contents, then I
1:15:08 search for that string...
1:15:11 it's in this chapter here...
1:15:15 then I go to that chapter with
1:15:17 C-s and M-y
1:15:21 and then - oops, sorry...
1:15:29 and then I will create a link to
1:15:34 to this string here in that page,
1:15:37 with the right number of spaces here...
1:15:40 so let me put that in the kill ring,
1:15:44 and M-h M-p...
1:15:54 and this is a pair of links that point
1:15:57 to this section in the manual.
1:16:01 Here we are...
1:16:07 and this one
1:16:09 opens that section in the manual
1:16:12 converted to text
1:16:16 so this was exercise (j).

;; k) [codeexample-1]

1:16:25 The next exercise -
1:16:28 exercise (k) -
1:16:34 is similar to that one, but it asks us to
1:16:37 create... uh, no, no, sorry -
1:16:40 this one is different!
1:16:44 This one says that we
1:16:47 have to start from this hyperlink and
1:16:50 then we have to find the source code
1:16:53 for a certain example.
1:16:57 We have to use this link here
1:17:01 to find that section in the source
1:17:03 of the manual
1:17:08 let me first create a link
1:17:16 to this string in this file... let me copy
1:17:19 it to my notes...
1:17:28 I have just just created something that
1:17:31 is useful to me, but that is not exactly
1:17:34 what the exercise asks for, that is
1:17:37 a link to a certain section
1:17:40 of the manual in the source code of the
1:17:43 manual. And now that I have this link
1:17:45 I'm going to search for
1:17:48 a certain \codeexample here - it is here -
1:17:56 now I have to run `M-x tik' here...
1:18:08 and then I will
1:18:11 change the body of this example
1:18:17 by the body of this \codeexample in the
1:18:20 manual - this one here.
1:18:23 Now let's test this.
1:18:31 It worked! Ta-da =)
1:18:39 We are almost at the end...
1:18:45 let me see what is the next exercise...
1:18:49 We were at exercise (k).

;; l) [codeexample-2]

1:18:52 Now we have to do exercise (l).
1:19:00 This one is similar to the to the
1:19:09 previous one, but instead of using tikzbody
1:19:12 we have to put this
1:19:14 string in another variable.
1:19:19 This links here searches for this
1:19:24 string in the source code of the manual...
1:19:38 I want this code example here.
1:19:54 and now I create a block like this one,
1:19:57 but this block here is going to to have a
1:20:03 an empty tikzbody,
1:20:07 so it's going to produce an empty figure...
1:20:10 and I'm going to copy this thing here
1:20:15 to the variable "hello".
1:20:19 The name is a bit silly, but the thing is
1:20:22 that in some of my early tests I just
1:20:29 did... one second...
1:20:32 I just did this with an empty tikzbody,
1:20:41 and when I run this block here
1:20:51 it just shows a "HELLO". That is...
1:20:56 I mean, it runs this this code here
1:20:59 outside the tikz block.
1:21:02 But...
1:21:05 the hint says to put this thing here in the
1:21:07 variable "hello".
1:21:12 If we want more information about
1:21:14 what does this does
1:21:17 we can go to the
1:21:20 to the source code in Lua...
1:21:23 sorry for the lack of colors, I forgot to
1:21:26 install lua-mode here...
1:21:28 but... the texbody is here, and before...
1:21:38 this block here defines a
1:21:40 tikzpicture inside the \scalebox,
1:21:44 and just before that I have a hello.
1:21:50 Anyway, the exercise asks for this,
1:21:54 and if you if you run this thing here
1:21:59 it runs these very low-level
1:22:05 commands here...
1:22:07 \pgfkeys is the low level way to
1:22:10 define styles in TikZ,
1:22:12 to make a very long story short.
1:22:19 So: the output of this is the result of
1:22:25 these two things here, as text.
1:22:31 This is super technical I'm not going to
1:22:33 explain that now...
1:22:35 But let me go to the
1:22:37 exercises again. We have just run the
1:22:41 exercise (l)...

;; m) [codeexample-3]

1:22:43 now we have the exercises (m) and (n).
1:22:52 (m) is also quite technical... people are
1:22:55 going to need something like this
1:22:57 if they need to run advanced examples
1:23:00 from the tutorial.
1:23:07 Let's first search for
1:23:10 "magnetic field" in the manual.
1:23:14 If we simply search for this, the
1:23:17 first occurrence of "magnetic field" in
1:23:20 the manual...
1:23:23 hm, it's probably in the page
1:23:29 565 or 566, so let me start by creating
1:23:34 links to this page of the manual.
1:23:38 Here we are. Let me copy them to my notes...
1:23:43 the string "magnetic field" appears here
1:23:47 in this figure...
1:23:53 and if the string appears here it's
1:23:56 because it also appears in the
1:23:58 source code, so let's search for it in
1:24:01 the source code.
1:24:03 Here it is: "magnetic field".
1:24:12 The exercise asks us to use this thing
1:24:16 here to find the first occurrence of
1:24:19 magnetic field in the source code of the
1:24:21 manual,
1:24:23 so we have to use this grep here.
1:24:37 Now let me create...
1:24:43 let me use this link here...
1:24:51 and now the exercise tells us to
1:24:55 create a TikZ block that runs this
1:24:57 example here.
1:25:00 But this example is not just a tikzpicture,
1:25:05 it also has some extra options -
1:25:08 here, just after the \begin{codeexample}.
1:25:13 If we just create a tikz block
1:25:20 that runs this thing here...
1:25:24 let me put that in the
1:25:28 in the tikzbody...
1:25:36 and let me try to execute this
1:25:39 thing here...
1:25:44 the show...
1:25:46 instead of saying "Success!!!" it says
1:25:51 that we had an error, and it does not
1:25:54 know how to explain what is that error.
1:25:57 So now we can run this thing here to
1:26:02 show the log of pdflatex...
1:26:07 sorry, of lualatex...
1:26:09 and the log says this:
1:26:14 is that it doesn't know how to run
1:26:18 "canvas (something)" - here.
1:26:23 it doesn't know how to run this.
1:26:26 And the trick is that we need to set
1:26:30 this "preamble=" somehow,
1:26:33 and the exercise says what we have to do...
1:26:38 it says that we have to load this
1:26:51 library here, and if we run this new
1:26:54 version of the eepitch block
1:27:01 now we have a "Success!!!" here, so
1:27:04 it has created a PDF correctly.
1:27:09 The log says the details,
1:27:12 but it's not very important now.
1:27:15 And ta-da! We were able to extract
1:27:19 that example from the manual and to
1:27:22 create an eepitch block that
1:27:27 runs that example.
1:27:32 so this was exercise (m).

;; n) [getmeaning]

1:27:34 And now we have a VERY technical
1:27:37 exercise. I mean,
1:27:41 most people who use latex are going to
1:27:44 find it completely mysterious, but
1:27:46 let me show it anyway.
1:27:51 The last exercise
1:27:53 says that
1:27:57 we have to execute the test blocks in
1:27:59 these files
1:28:02 this one here goes to the copy
1:28:06 of this file in my site - it uses wget...
1:28:10 and this one goes to the local copy.
1:28:13 Let's use this one.
1:28:21 Let me spend a few seconds more to to
1:28:25 load lua-mode, because this thing is
1:28:28 going to be much more easier to
1:28:30 understand if I...
1:28:37 oh no -
1:28:41 I'll have to cheat a bit. One second.
1:28:47 Hm,
1:28:50 you are not expected to understand this...
1:28:58 let me run this thing again...
1:29:01 Now this is going to load all packages from
1:29:04 MELPA, and it's going to display them...
1:29:09 it takes a long time...
1:29:24 wow, it's taking much longer than I
1:29:26 expected...
1:29:34 whoops...
1:29:46 let me install this thing...
1:29:57 it's installed.
1:30:00 Hm,
1:30:05 I forgot to to copy the last exercise to
1:30:10 to my TODO file - to my notes...
1:30:14 now I've copied it.
1:30:16 Now if I open the local copy of this
1:30:21 Lua file here it's probably going to
1:30:23 be able to fontify everything
1:30:27 correctly...
1:30:28 no, it didn't!
1:30:30 Anyway, sorry...
1:30:32 sorry for not having installed
1:30:36 lua-mode before. anyway now we have the
1:30:38 colors, and we can see clearly
1:30:41 that this thing is a big comment and
1:30:43 this thing is a test block,
1:30:45 and we can run this test block here to
1:30:48 understand how these
1:30:51 functions work... and this is the super
1:30:54 technical thing that I want to explain.
1:30:58 This line here
1:31:01 says that
1:31:04 we will
1:31:06 prepare a .tex file that will not
1:31:09 generate a PDF, because it will stop
1:31:11 before... it will stop in the middle of the
1:31:13 execution when lualatex is trying to
1:31:17 compile it, and it will stop because it
1:31:21 will run a REPL, and not the default
1:31:24 TeX REPL... it will run a
1:31:26 REPL in Lua
1:31:28 that is defined here... here we have
1:31:33 an explanation...
1:31:37 it says that when we run this
1:31:42 then
1:31:43 texbody will include this block of
1:31:46 code here...
1:31:50 and this block of code will
1:31:56 load a certain Lua file into lualatex,
1:32:00 and then it will run this \repl,
1:32:02 that is defined in a very mysterious
1:32:05 way.
1:32:07 Anyway let's run that in practice. If
1:32:11 we execute this,
1:32:14 then...
1:32:15 I have just saved the the .tex file, I
1:32:19 have not asked
1:32:21 my Lua files to to run latex on
1:32:24 it...
1:32:25 and now I'm going to run lualatex
1:32:29 on it inside a shell - here...
1:32:33 inside another REPL that is running a
1:32:35 shell.
1:32:36 if I run this then it
1:32:38 starts the compilation and then it gives
1:32:41 this prompt here, and this prompt here is
1:32:45 a Lua prompt.
1:32:55 And
1:32:57 now I'm going to run these things here...
1:33:02 for example, printmeaning("newpage") will
1:33:05 run a certainly mysterious thing, and it
1:33:08 will say that the definition of
1:33:11 \newpage is this thing here.
1:33:18 So \newpage is a
1:33:20 TeX macro that is defined in this way,
1:33:23 and this printmeaning(...) here will do
1:33:28 something similar, but with it will
1:33:32 use a very low level trick to discover
1:33:35 what is the current meaning of
1:33:38 "rounded corners" for TikZ...
1:33:41 so "rounded corners" has this definition
1:33:43 here... and
1:33:47 this thing is the same thing but in
1:33:49 a shorter version, and this thing is the
1:33:52 thing in an even shorter
1:33:55 version, and this one
1:34:00 shows the definition of "right", that
1:34:03 we use sometimes to specify
1:34:06 how labels have to be placed.
1:34:11 So this is a way to inspect definitions
1:34:14 from inside the Lua REPL. It's something
1:34:16 super tricky and
1:34:20 at the end of this this page here...
1:34:26 I'm not sure if if the links are already
1:34:29 there, but I'm going to explain...
1:34:31 uh, to give some links about how these
1:34:34 things work.
1:34:37 Hm, no I don't have the links right now...
1:34:42 I had to ask some questions at
1:34:46 StackExchange and StackOverflow to
1:34:49 understand how to do these things,
1:34:50 and...
1:34:54 the whole story is that I wanted to
1:34:56 do something much more complex...
1:35:00 I wanted to be able to expand a
1:35:04 \pgfkeys{...} from this REPL, and then I
1:35:07 asked the question, and then people
1:35:08 explained to me why that was impossible...
1:35:13 so what we have
1:35:16 here is something much more humble...
1:35:19 instead of of expanding
1:35:24 definitions using PGF
1:35:27 this thing here simply
1:35:31 shows what is the current definition
1:35:33 without any expansions.
1:35:37 This is a long story, it's super technical,
1:35:39 I'm going to explain more about this in
1:35:42 the page at some point, but it's...
1:35:45 I mean, here -
1:35:47 no, I mean here - but it's not ready yet.
1:35:51 And...
1:35:57 so, that's it - this finishes all
1:36:02 the exercises. Let me
1:36:05 stop the video now,
1:36:07 and then I'm going to put more material
1:36:10 in the page, and I'm going to add
1:36:12 subtitles to this video, so that people
1:36:14 can use the subtitles to
1:36:17 see how to perform the
1:36:21 exercises...
1:36:23 So, that's it. Bye!!! =)