Lecture 3: Editors (vim) (2020)

Okay, cool. So, welcome to the third

lecture of the missing semester of your

si a second today we're going to be

talking about text editors this is a

topic that I really like I think it's

one of the most valuable topics that

we're teaching in this class because as

programmers you spend so much of your

time editing text editing programs that

if you invest time into making yourself

more efficient at doing this you'll save

a ton of time probably hundreds of hours

over the course of your undergrad or

over the course of your career so text

editors are a little bit different than

other programs you might use to edit say

things like English prose because

programming is different than writing

English prose when you're programming

you spend a lot of time reading what

you've written you spend a lot of time

navigating around a buffer and you spend

a lot of time making little edits to

code all over the place rather than just

writing in a long stream like you do

when you're writing an essay or

something and so it makes sense that

there different programs for these

different purposes right so yeah things

like Microsoft Word for writing essays

and things like vim and Emacs and vs

code and sublime for writing code so the

way you learn a text editor and become

really good at it is you start with a

tutorial and so that's basically going

to be the function of today's lecture

plus the exercises we've given you and

then after the tutorial you need to

stick with the editor for all your

editing tasks and when you're learning a

sophisticated tool so today we're going

to teach you vim which is one powerful

editor that a lot of programmers use

when you're learning such a

sophisticated tool it may be the case

that initially switching to this tool

slows you down a little bit when you're

programming but stick with it because

I'd say that in about 20 hours of

programming using a new editor you'll be

back to the same speed at which you

programmed using your old tool and then

after that the benefits will start and

you'll get faster and faster as you

learn more with these sophisticated

programs like them it takes not way too

long to learn the basics but a lifetime

to master and so throughout the time

you're using this tool make sure you

look things up as you go if you ever get

to a point where you're like oh this is

a really inefficient way of doing things

is there a better way the answer is

almost always yes because these text

editors were written by programmers for

programmers and so of course like the

peep

I wrote these tolls ran into the same

kinds of issues and fixed them so that

you don't need to deal with these

anymore and so yeah as you're learning

make sure you look things up as you go

either use Google or feel free to send

us emails if you have questions or come

to office hours and we'll help you

figure out how to do things really fast

so as far as which editor to learn in

previous iterations of this class we

actually avoided teaching a specific

editor because we didn't want to enforce

our opinions on you guys but we actually

think that it's really useful to teach

you how to use one particular tool and

use it well and so people have really

strong opinions about editor so you can

see the course notes for more links on

this topic looking at which editors have

been popular over the years Stack

Overflow I'm sure you've all heard of

that does a survey every year asking

developers various questions and one

thing to ask is which TextEdit Derk do

you use and it seems to be that

currently the most popular kind of

graphical editor is vs code and the most

popular editor that is based within a

command line interface is vim and so

we're going to be teaching you vim and

there a couple reasons for this one is

that all the instructors so me John and

Jose use vim as our primary editor and

we've been doing this for many years and

we've been very happy with it

and we think that there are a lot of

interesting ideas behind them so even if

you don't end up using this particular

tool in the long term I think it's

valuable to learn these ideas and also a

lot of tools have actually been really

excited about the ideas in vim and so

they support a vim emulation mode for

example vs code what's apparently the

most popular editor in use today

supports vim bindings and this vim

emulation mode as of now has like 1.4

million downloads and as you'll see over

the course of this lecture a lot of

different tools like including your

shell including things like the Python

repple and like Jupiter notebook and all

sorts of other things even your web

browser can support of emulation mode

and so yeah we're going to be teaching

you this really neat tool today and in

this lecture we can't really cover all

of them right it's a very powerful tool

but our goal is to teach you and the

core philosophy of them like the really

neat ideas behind it and then in

addition to that some of the basics like

how do you open a file close a file

navigate around a file make edits and

things like that and

you may not remember every single little

detail from this lecture because we're

gonna go pretty fast through some of the

material but it's all in the lecture

notes and then the exercises actually

give you links to some tutorials and

things so I highly recommend that you

actually go through all the exercises at

least the non advanced exercises any

questions so far great okay so one of

the really cool ideas behind them is

that vim is a modal editor what does

this mean modal comes from the word mode

and this means that vim has multiple

operating modes and this is kind of

developed from the idea that when you're

programming there often times where

you're doing different types of things

like sometimes you're reading code

sometimes you're making small edits to

code like you're finding a particular

point like changing a little thing

somewhere sometimes you're just writing

a lot of code in one go like suppose

you're just writing a function from

scratch and so there's different

operating modes for doing these

different types of things and so I'm

actually want to write this down on the

blackboard so I'll have a useful thing

to refer to later so when you start vim

up it starts up in what's called normal

mode and in this mode all the different

key combinations behave in one way and

then there are different key

combinations that switch you between

normal mode and other modes which change

the meaning of different keys so for the

most part you'll be spending most of

your time in vim in normal mode or what

is called insert mode and to go to

insert mode you press the key I for

normal mode and to go from insert mode

back to normal mode you press the Escape

key a little note on notation because

we'll need this later in the notation

I'm going to be using in this lecture

and what's also in the lecture notes and

what vim uses to give you feedback they

have a couple different ways of talking

about different keys so when they're

talking about bare keys like just the

eye key on your keyboard they'll just

say eye but for a different key

combinations like when you press control

and something like say control V it's

notated in one of like approximately

three ways one way that can be notated

is a caret and then the control

character so this is control V another

way this might be written I think we've

written it this way in

lecture notes as control-v this is

probably the one you're more used to

seeing and then in some parts of them

this is written as angle brackets C - V

close angle bracket so just a little bit

of notation that will be useful later

so yeah vim has a couple different modes

where normal mode is designed for

navigating around a file reading things

going from file to file things like that

and then insert mode is where you type

in text so most keys that you press here

will just go into your text buffer where

as keys that you press here are not

being put into the buffer and instead

are used for things like navigation or

making edits and actually the picture is

a little bit more complicated than this

there are a whole bunch of other modes

and I'm just gonna write them down here

because we'll have them here to refer to

later and so if it also has a replace

mode for rather than inserting text and

kind of pushing what's ahead of it

forward it will overwrite text and then

it has a bunch of different modes for

selection so it has a mode called visual

mode and then it has visual line and

visual block this one is enter via the R

key this was entered via the V key this

one is entered via shift B and this one

is entered via control V and then

there's the command line mode which is

entered via the colon key

okay so now that we have that on the

board to refer to later we can actually

try some of this out all right so one

thing we noticed looking at that picture

is that to go from normal mode to any of

the other modes we press some key but to

go from any of the other modes back to

normal mode where we spend a lot of our

time we use the Escape key on our

keyboard so for this reason since you

under pressing the Escape key a lot when

using vim a lot of programmers rebind

one of the keys on their keyboard to be

escape because it's really inconvenient

to reach up with your left pinkie to

press that tiny little Escape key in the

corner of your keyboard and so a lot of

people use the caps lock key instead so

it's right there in the home row and we

have some links in the lecture notes for

how you can do this key rebinding okay

so now that we've talked about kind of

one of the core ideas of vim the idea of

modal editing we can talk about some of

the basics like how do you open up this

text editor how do you open file save

files and things like that and so this

is a command line based program although

there are some graphical variants and

the way you start this program is by

running vim one thing you might notice

is that in the bottom left corner of my

screen they actually saw what I just

typed this will be useful later in this

lecture where I'm actually typing in

commands for vim and I'll be saying what

I'm typing but you'll also see it on the

screen so if I press ctrl C see it says

ctrl C over there is that text big

enough for everybody to read great okay

so the way we open vim is just by

running the program vim on our command

line and this comes pre-installed on

most systems and if you don't have it

you can install it using your package

manager vim can also take an argument if

we want to use it to edit a particular

file instead of just opening up the

program then later opening a file so for

example I have a file in this directory

this is actually the lecture notes for

this lecture so I can do vim editors MD

and press ENTER and then boom them is

started and then in this lecture I'm not

running vim in the completely Exton I've

configured a couple of things that

behave a little bit nicer by defaults

little things like having line numbers

on the left or having some more status

information on the bottom and if you

want to start with this default

configuration we have a link to this in

the lecture notes so you can get a

slightly more sane config by default. So,

once you've opened Vim, what do you do?

Well, as I said earlier, Vim starts in

normal mode, so if I just start typing

letters like, say, type X it didn't insert

X into the buffer. You can see the cursor

up in the top left: it actually deleted

one of the characters. That's because I'm

in normal mode, not insert mode. So insert

mode is basically what you're used to with

all the other text editors you've used

in the past, where there's a cursor

somewhere, you press the character, and it

just goes into your buffer. I'm instead

in vim you start a normal mode and you

can press I to go into insert mode so

see I've pressed I and then in the

bottom left notice that it says - -

insert the bottom left always tells you

what mode you're in unless this normal

mode in which case it's blank and now

that I'm an insert mode if I press the X

character for example see it just gets

inserted into my text buffer and I can

backspace over at type other stuff and

now my text editor kind of behaves like

you'd expect any other program to behave

so from this point how to go back to

normal mode if I want to stop inserting

characters. Yes, exactly. I press escape.

And, that's the symbol my keystroke

visualizer uses for escape, so

just be aware of that. And then, Vim has

this idea, that using the mouse is

inefficient, like your hands are on the

keyboard, moving your hand over to the

mouse takes a lot of time, right, like you

don't want to waste those couple of

milliseconds while you're programming,

like in the middle of things. So, instead,

all Vim functionality can be accessed

just through the keyboard. And, it's all

sorts of things you might be used to

doing like opening files by going, like,

file open, or file save, or things like

that, or instead access through the

keyboard. And, how is that done? That's

done through one of the other Vim modes

that are on the board over there. In

particular, through command line mode. So,

if you're in normal mode, and you press

the ":" key, you'll notice that the

cursor - I guess my visualizer is covering

the thing right now but it's gone - the

cursor jumps to the bottom - the bottom

left - and it shows that ":" I just typed.

Now, I can type in a command. So, you can

think of this almost like the command

shell that we've talked been talking

about over the last few days, except this

is Vim's

command shell, so you give Vim commands

here, instead of shell commands. And

there are a bunch of built-in commands

that do all the things that you're used

to. Like, for example, one command that you

might want to know is how to quit this

editor. You might notice that if you're in

normal mode, I can press "Escape" to go

back from command line mode to normal

mode, and I press "control C", unlike what

happens to a lot of programs, this doesn't

quit Vim. So, how do I quit Vim? I can

press ":", and then go into command

line mode, and then I can type in the

command "quit". "Q-U-I-T". You'll see that I

- maybe I should move this over to the

middle or something - see, it says ":quit"

and I press ENTER, and it quits Vim. I can

open Vim up again. There's actually a

short form for this command, just ":q", and

that'll do the same thing. And, there are a

bunch of other useful commands like this.

So, some other handy ones to know are

how do you save a file? So, suppose I make

some edits here, like "hello world".

So, I pressed "i" to go into insert mode - or

let me redo that - I press "i" to go into

insert mode. Right now, I can use the down

arrow to... I think I've slightly I

should fix that. Can you fix the config,

actually, John? Never mind that.

Okay, so, suppose I go down to this line,

and I press "i" to go into insert mode, and

type in some text, and then press "escape"

to go back to normal mode. Now, how do I

actually save this file? Well, there's

another command for that. So, ":" to go

into command mode, and then I can type "W"...

...and press "Enter". "W" stands for write. And,

it says in the bottom "editors.md"

whatever blah blah written. And, so, this

means it saved the file and so now if I

":q" to quit and open the same file,

again, you'll see that the changes have

been persisted. There are a couple other

there's... So, there's a ton of different

Vim commands that are useful for

different reasons. But, I'll just explain

a couple more to you now. One command

that's really useful is help. ":help"

And you can do ":help", and then type in a

particular key, or a particular command,

and get help for that keystroke or that

command. So, if I want to know what

":w" does, I

can do : help : W, and that'll give me

the documentation on : w or : write. If I

do : q, it'll close this window and bring

me back to where I was before.

And, notice that ":help :w" is different

from ":help w", because the W key is the W

that, like, when you're in normal mode and

press W, what happens is just the W key

here without the ":".

And, if I look for help for ":w", that's

the help for the W command. So, now you

basically have the bare fundamentals

needed to use them. right? You can open

the editor, use it to edit a particular

file, press "i" to go into insert mode and

type in some text, press "escape" to go

back to normal mode, and then :w to save

your changes, :w to quit. So, like already

you have the bare fundamentals necessary

to edit files using Vim, albeit somewhat

inefficiently. So, any questions so far?

Yeah in the back. Yeah so the question is,

What's the benefit of the

normal mode? And, we'll talk about that in

more detail, in like five minutes.

But, in short, insert mode is just for

typing in text. So, I'm in insert mode, I

can type in text. But, when I'm

programming, I actually spend a lot of

time moving around my file making small

little changes. So, I go here and like, oh

maybe I want to change this HTTPS link to

an HTTP.

I can make like small point edits, things

like that, in normal mode. And we'll see a

whole lot more of that in about five

minutes. Good question!

Any other questions? Okay cool. So, moving

along, one other thing that's kind of

useful to know, I think, is, at a high

level, Vim's model of

buffers versus windows versus tabs. So,

it's probably the case that whatever

program you were using before, like

Sublime Text or VS Code or whatever,

you could open multiple files in it,

right, and you could probably have

multiple tabs open and have multiple

windows open of your editor. So, Vim also

has a notion of those different things.

But, its model is a little bit different

than most other programs. So, Vim

maintains a set of open buffers - that's

the word it uses for open files - and so,

it has a set of open files, and then kind

of separately from that, you can have a

number of tabs, and tabs can have windows.

The kind of weird thing which makes Vim

a little bit different than the

program you've probably used in the past is

that there isn't necessarily a

one-to-one correspondence between

buffers and windows. So, one thing I can

do, for example, here - and we'll show you

the key combinations and stuff for this

later - but one thing you can do is create

two different windows. So, I have one

window up here, and then one window down

here. And, notice that the same files open

in both windows. So, if I make some edits

over here, they actually happen in the

bottom window, as well, because it's the

same buffer that's open in both windows.

And, this is kind of useful, for, say,

looking at two different parts of a

single file at the same time. Like, so you

want to be able to look at the top of a

file, say at an import to your program,

while you're down below, working

somewhere else. So, this is one helpful

thing to keep in mind, that Vim has this

idea of - there are a number of tabs, and

each tab has some number of windows, and

then each window has, uh, corresponds to

some buffer. But, a particular buffer can

be open in zero or more windows at a

time. Just one thing that confused me

when I was initially learning Vim, so I

want to explain that early on. And then,

the ":q" command, which we talked about

earlier, is not exactly quit. It's kind of

"close the current window", and then, when

there are no more open windows, Vim will

quit. So, here, if I do ":q", it'll only

close the window, I think, on the top here

because that's the one I was in, and, now,

the remaining window becomes fullscreen.

I can do : Q again to close this. Now we're in

the second tab that I'd opened. If I do :Q

a final time, okay, now, Vim exits. And if

you don't want to press ":q" way too many

times... Okay, so, here I have three split

windows. If I do ":qa", for quit all, it

closes all the open windows.

All right, so, now, to answer your question of

"What is normal mode actually for?" This is

another, really cool idea in Vim, and I

think this is actually, like, the most

fundamentally interesting idea of this

program. It's that, like, you're all

programmers, you like programming; Vim has

this idea that Vim's normal mode, like,

Vim's interface, itself, is a programming

language. And, let me repeat that.

That's like a kind of fundamentally

interesting idea: the interface is a

programming language.

What does that mean? It means that

different key combinations have

different effects, and, once you learn the

different effects, you can actually

combine them together - just like in a

programming language - you can learn

different functions and stuff and then

glue them all together to make an

interesting program. In the same way, once

you learn Vim's different movement and

editing commands, and things like that,

you can talk to Vim by programming Vim

through its interface. And, once this

becomes muscle memory, you can basically

edit files at the speed at which you

think. Like at least for me, I don't think

I've been able to do this with any other

text editor that I've used in the past,

but this one gets pretty close. So, let's

dig into how exactly normal mode works.

So, you can try to follow along with this,

like, open up some random file in Vim, and

follow some of the key combinations I

type in. So, one basic thing that you

might want to do, is just navigate around

a buffer. Like, move your cursor up/down/

left/right. And, so the way you do that in

Vim, is using the hjkl keys, not the arrow

keys. Though they do work by default, try

to avoid them, because you don't want to

have to move your hand all the way over

to the arrow keys. Like, there's a ton of

time you're wasting, right? HJKL is right

on the home row. And, so, J moves down, K

moves up, H moves left, and L moves right.

And, this may seem a little unintuitive

now; there was some historical reason for

it, like, the keyboard the original vi

developer used had the hjkl keys, like,

labeled, and arranged in a way that made

this more reasonable. But, this will very

soon become muscle memory. So, this is the

basic way you can move your cursor

around while in normal mode. Now, what

else can you do? Well, if we had to move

around files like this, it'd be really

slow. We don't want to have to

hold down these keys, and like, wait for a

long time for Vim to do its thing. And

so, there are all these other, different

key combinations for doing different

movements.

Also, by the way, this is all in the

lecture notes, so you don't need to

memorize every single key and its

meaning right now. Just try to understand

the overall idea that Vim's interface is

a programming language. So, another thing

you can do is press the W key. This moves

the cursor forward by one word. And then,

similarly, the "B" key moves the cursor

backward by one word. So, this allows

slightly more efficient movement within

the line. There's also the "E" key for

moving to the end of a word. I'm going to

move this over a little bit. So, if I'm

here, for example, and I press the "E" key

it'll go to the end of this word, end of

this word, end of the next word and so on.

You can also move by whole lines, so zero

moves to the beginning of a line, dollar

sign moves to the end of a line, and the

caret key moves to the first non-empty

character on a line. So, let me find one

of those, for example. So, here, my

cursor's right here; if I press 0, my

cursor goes to the beginning of the line,

dollar sign, end of the current line; and

if I press caret, where, like, on what

character will the curser end up? Can

anybody guess? So, caret goes to the first

non-empty character on a line, kind of

like Regex caret. Yeah, exactly! It goes

to this dash. Let's talk about some more

movement commands. There're ways to

scroll up and down in a buffer, so

control U goes up, and control D scrolls

down. So, this is better than holding down

the K or J keys, for example. This is a

lot slower than moving by entire pages.

Control D and control U. There's also

ways to move by the entire buffer. So,

capital "G" moves all the way down... "gg"

moves all the way up. Some of these

movement keys are mnemonics; so, they're

like, a little bit easier to remember for

that reason, right, like, "W" is word, "B"

is beginning of word, E is end of word. Those

all seem pretty logical. 0, caret and

dollar, kind of inspired from Regex, so

those make a little bit of sense. There's

some other ones that, like, don't

necessarily make way too much sense, but,

there are only so many keys on your

keyboard, so what are you going to do? For

example, the "L" key moves your cursor to

the lowest

line that's shown on the screen. "L" for

lowest makes sense, M for middle, and then H for

highest, I guess. And, there's a whole

bunch of other interesting movements

like this. So, we're obviously not going

to be able to cover all of them right

now, but you'll be able to go through

them in the Vim tutor exercise, which is

exercise number one for this lecture.

Some other ones I want to talk about now -

maybe I'll talk about one more. There's

another movement called "find". This is

also kind of useful. Suppose I'm on this

line, and I want to jump to the first

character that equal's to... Like, I

want to jump to the first "o". I can press

"fo", and my cursor moves to the first

"o". I've like, found "o". I can do fw and

it'll move to the first "w", which I think

is right here. fc: find the first C. I can

also do the same thing, but backwards. If

I do capital F, w, I can find the W that's

before it. Capital F, s: find the s that's

before that. And then, there's a variant

of f, for find: t for to, so I can jump to

O, and it jumps, like, until it's found o.

But not on top of it, right before it. And

capital T say, t, jumps backwards to the t

except not all the way on top of it, one

character before. And, so, you can already

see that idea I talked about, of like, Vim

is a programming language; you can, like,

compose these commands. "F", and "T", are

"find", and "to", and you can say "find" a

particular character, or jump "to" a

particular character. So, those are a

couple of Vim movement commands. So, any

questions about those so far? So this is -

yeah, question? Or... no? Okay, cool. So,

those are Vim movement commands.

This is how you can navigate around a

file quickly in normal mode. Now, another

category of useful commands are editing

commands. So, one we kind of already

talked about is the "i" command

for moving from "normal" mode to "insert"

mode, where you can start just writing

text. So, suppose I go up here and I press

"i". Now I can type in whatever text I want

"Hello world", "enter". Then, press

"escape" to go back to normal mode, and

I've made a change to my buffer. But,

there are a whole bunch of other

commands for making efficient edits

that makes sense for when you're dealing

with programming languages. So, one useful

command that I accidentally used earlier,

before teaching you about it, is the "o"

command. So, suppose my cursor is, like,

over here, and if I press "o", from normal

mode, what it does, is it opens a new line

below where my cursor is.

That's what "o" stands for. And it, so it

creates a new line, and it put me into

insert mode. So, now I can start typing in

some text, press escape, and go back to

normal mode. And then, just like the "o"

command, there's a capital "O" command, so

if I'm here and I do capital "O", it puts

me into insert mode above where I

currently am. There's another Vim command

for deleting things. So, suppose my cursor

is, like, on top of this word right here,

and I press the D key. "D" for delete. Oh,

nothing happens; turns out that the D key

needs to be combined with a movement

command. So, remember we just talked about

different movement commands, like hjkl,

and, like, word, and backward word, and

things like that.

So, I press D. Whoops. I press D and I can

press W, and it's deleted a word. So, let

me undo that. Undoing in Vim is just u for

undo. So, notice my cursor's right here. I

do "dw": it's deleted a word. I can move

around, and then delete another word.

Suppose I'm - uh, keeps getting in the way

Suppose I'm, like, somewhere in the middle

of a word, and I want to delete to the end

of a word. Any guesses for what

combination of keys I'd use for that? "d"

and what? de, exactly. Delete to the end of

the word. Another useful editing command

is the c command. c stands for change. So,

change is really similar to delete,

except change puts you in insert mode,

because, like, I want to delete a thing,

but change it to something else. So, if

I'm here, and I do "ce", it's like, change

to the end of the word. And, it gets rid

of the contents until the end of the

word, and notice it put me in insert mode.

So now, whatever characters I type go

into the buffer. If I press "escape", I go

back into normal mode. And so, c and d are

analogs: they both take motions as

arguments. And, they will either delete

that motion, or change

that motion. So, for example, if you press

the c key, there's also this pattern that,

if you press a particular editing key

twice, it'll have that effect on the

given line. So, if I press "dd", that

deletes the line. If I press "cc", that

deletes the given line, but puts me in

insert mode, so I can replace it with

some other line. We'll cover a couple

other, uh, editing commands, because then

later we'll see how all these things

interact together. So, another useful one

is the x command. So, suppose my cursor is

over some particular character. If I

press "x", it just deletes that

character. There's another command called

r. If I'm over a particular character, and

I press "r", it takes another character as

an argument, and it replaces that

particular character with some other

character. And, I'll cover a couple more

editing commands. So, I think one I

talked about a moment ago - but, of course

you can undo changes you've made in Vim.

And the way you do that is by pressing

"u" while you're in normal mode. So, u for

undo is pretty easy to remember. So, I

press "u" a whole bunch of times; it's

undone all the changes I've made. And

then, the opposite of undo is, of course,

redo. And, the binding for that in Vim is

control + R. All right, one other editing

command I'm going to talk about is copy

and paste because-oh yes, question? That's

a - that's a great question! So, the

question is, "Does 'undo' undo everything

you've done since you've gone into

insert mode, or just the last character?"

It's - it's actually a little bit more

complicated than that.

"Undo" does, like, undoes the last change

you've made. So, if you went into insert

mode, and typed in some stuff, and went

back into normal mode, and then press "u"

for "undo", it'll undo all you've done in

insert mode. But, if you've done some

other type of editing command, like, say I

press "x" to delete a character... If I do

"u" for undo, it'll just undo that change

that that editing command made. Now, does

that answer the question? (Yeah) Great any

other questions?

Cool. So, I'll talk about copy and paste

as well, because that's a popular one. The

y command stands for copying, and the p

command stands for pasting. y for "copy",

because, yank. Like, that's the word they-

that's the terminology that

Vim uses for copying. And, these commands

are- y also takes a motion as an argument.

So if I do like, yy, it copies the current

line. And, if I press "p" for "paste",

notice that now these two lines are

identical, because I've just pasted a

line below. "u" for "undo". But if I do

something like "yw", it's copied the word.

And then I can do "p", and it just pasted

that word again,

right where my cursor was. One useful

thing, especially in the context of copy

and paste, is to be able to select a

block of stuff and copy it, right? Like,

this is probably how you used copy and

paste in whatever editor you were using

before. And so, that's where we get into

the visual modes. So, these are another

set of modes that are all related to

each other, and that can be reached from

normal mode, and they're used for

selecting chunks of text. So, one mode is,

just, regular visual mode. You can enter

that by pressing v. And then, once you're

in this mode, you can use most of the

regular normal mode commands to move

your pointer around. And it selects

everything in between. So I can use, like,

hjkl just to move the cursor, or I can

use "w" to move by words, or different

things like that, and it will select a

block of text. And, once I've selected

this block of text there are a whole bunch

of different types of useful things you

could do with it. One of the most popular

things to do is copying this. So, once

I've selected, I can do y to copy, and it

puts me back into normal mode. And now,

it's copied this to the - to the paste

buffer. And then if I go somewhere else,

and press "p", it pastes in that whole

chunk of text I copied. And it's similar

to visual mode, which selects kind of a

contiguous stream of text. There's visual

line mode: that can be reached by

pressing capital V, and that selects

whole lines at a time. And then there's

VISUAL BLOCK mode, which can be selected

by pressing "control" + " V", and that can

select rectangular blocks of text. So

this is something your old editor

couldn't do. Alright, so, there's a lot

more Vim editing commands to learn.

There's lots of, like, really weird and

fancy things. Like, for example, the tilde

command changes the case of the

character, or the selection that you've

currently selected. So for example,

I can take this, like, Visual Studio Code,

and flip the case on the whole thing, by

selecting it and pressing tilde. And,

there's a whole bunch of other things

like that; they get more and more

esoteric as you go. So, we're not going to

cover all of those, but you'll get to

those in the exercises. So, those are Vim

editing commands, and a lot of them can

be composed with movement commands. So,

any questions about either of those so

far? Cool. So, moving along, another

category of things -of commands- that are

mostly relevant to normal mode are

counts. So, you can give them a number, to

do a particular thing, some number of

times. So suppose my cursor is here, and I

want to move down, like 1 2 3 4 lines. One

way I can do that is by pressing "j" four

times - go down four times. "kkkk" goes

up four times. But, rather than pressing a

particular key again, and again, I can use

a count. So if I press "4", "j", it does j

four times, right?

Vim's interface is a programming

language. If I do "4k", it moves up four

times. If I am here, and I press "v" to go

into visual mode... Okay so now I can move

my cursor around, and select blocks of

text. I can do, like, "eee" to select a

couple of words, but, I could also go back

here -v for visual mode- and press three e

to select, like, three "ends of words"

forward. And then of course these can also

be combined with editing commands. So,

like, suppose I want to delete seven

words. I can do that by moving my cursor

somewhere, and doing "7dw". Seven delete

words. And so, this is particularly useful

for things like, suppose my cursor is

somewhere on the screen, and I'm looking

somewhere else on the screen, or, I want

my cursor to go to that particular line.

Notice that I've set up relative line

numbering on the left. So, wherever my

cursor is, it shows the current line

number, but everywhere else, it's just the

offset from where I am. Now, suppose my

cursor is here, but I want to move down

to the like "Microsoft Word" down here, so

that's eight lines down. So, what

combination of keys would I press, to do

that? Like, what's the most efficient way?

Yeah, exactly!

Let's try that out-8j-and my cursor moved

down to this line.

Okay. And then, one, final category of key

meanings in Vim is something called

modifiers. So we have, so far, movement,

edits, counts, and, finally, we have

modifiers. So, modifiers kind of change

the meaning of a movement command a

little bit. And, a couple modifiers that

are especially useful are the "a" and "i"

modifier. So, a stands for like around and

"i" stands for inside. And, to see where

this is really useful, I can move my

cursor to somewhere like here, for

example.

So, hopefully, most of you are familiar

with markdown syntax - and if not it

doesn't matter too much. Uh, this is a

link in markdown; it's a text rendered in

square brackets, and then the link in

parentheses. Suppose my cursor is inside

here, and I want to change the text

corresponding to this link. Well, one way

I could do that is, like, move back here

with b, and, like, 2dw, and then "i" to go

into insert mode. That's one of the

many ways I can make this change, and I

can type in whatever other thing I want -

u to undo, u to undo. Another way I could

have done that is change two words - "c2w"

- and then type in some other text. But,

one final way I could do the same change

is using the modifier commands to talk

about how I want to interact with these

different types of grouping things like

parentheses and square brackets. So, one

final way of doing this is change inside

square brackets-"c" "i" "["-and that puts

me into insert mode, after deleting the

contents that are inside the brackets. So,

do you see how we can take all these

different ingredients, like we talked

about "change", and we could combine that

with different movement commands. We

talked about inside, how it's a modifier.

And then we talked about, uh... we didn't

talk about parentheses. But, if your

cursor is hovering over a different, uh,

different types of grouping things like

parentheses, or square brackets, you can

press the percent movement key to jump

back and forth between matching

parentheses. If I go over here and I do d,

i, (, I can delete the contents

inside these parentheses. And so, those

are Vim, uh, modifiers. I guess we talked

about i, but we didn't talk about a. If I

do "da(", it deletes a whole,

like parenthesized group including the

parentheses so I is inside

is around or including all right so

those are basically the different

categories of things you can combine

together, when interacting with Vim's

interface. So, any questions about that or

the overall idea of this interface being

a programming language? Cool. So, let's do

a quick demo, to kind of demonstrate the

power of this editor. And, it will kind of

help us see how this tool can work

really fast and kind of match the speed

at which we think. So, over here is a very

broken "fizzbuzz" implementation that

doesn't actually print anything.

Uh, hopefully, most of you have heard of

"fizzbuzz" - if not, I'll explain it super

briefly. Uh, "fizzbuzz" is a programming

exercise where you print the numbers 1

through n, but when the number is

divisible by 3, you print fizz - when it's

divisible by 5, you print buzz. And, when

it's divisible by both 3, and 5. you print

fizzbuzz. And, if none of those apply, you

just print the number. So, you should

print like 1, 2, fizz, 4, buzz, and so on.

But, if I run this program, it doesn't

print anything here I have them on the

left in just a terminal on the right ok

so there's a bunch of issues with this

one is that main is never called so

let's start off with fixing that so

here's how I would make this change and

notice how few keystrokes this requires

capital G means go to the bottom of the

file o opens a new line below and now I

can just type in stuff so I'm an insert

mode okay so I've typed in whatever

change I want to make escape to go back

to normal mode if I do : W so command

mode right let me go back here okay now

at least my program prints something

when I run it another issue with this

program is that it starts at 0 instead

of 1 so let's go fix that so I want to

go over to this range whoops this range

thing and it shouldn't be going from 0

to limit it should be going from 1 to

limit plus 1 1 command which I didn't

show you about is how you search in vim

so you press forward slash

to close this and restart it if you

press forward slash it starts search so

if I type in range enter my cursor goes

from wherever it was before to the first

instance of range it found so it's a

really efficient way of moving where I

want to move WW to move forward two

words I to go into insert mode add the

one comma space escape I'm back in

normal mode this is a very common

pattern in vim you stay in normal mode

you go somewhere you go into insert mode

you make a tiny change and you jump

right back to normal mode like normal

mode is home and that's where you should

be most of the time I also want to add a

plus one so e to go to the end of this

word a for a pend plus one escape

alright fix that problem and other issue

is that this program prints fizz for

both divisible by three and five so

let's fix that slash fizz searches for

fizz been oppressed and it goes to the

next match see I press E I quote changes

what's inside the quote so it's deleted

the fizz and put me in insert mode right

in between those two quotes and I can

type in whatever I want

escape to go back to normal mode so

great I've fixed that particular problem

another problem with this program is

that it prints fizz and Buzz on separate

lines for multiples of 15 so let's let's

go and fix that let me go down to this

line here

one way I can don't actually worry about

like the actual contents of this program

like this some stupid program that

doesn't matter pay attention to what

keys I'm pressing in vim that allow me

to make changes to this program really

efficiently so my cursor is on this line

i press dollar to go to the end of this

line i for insert mode okay and i'm

typing some stuff escape to go back to

normal mode now I want to make the same

change the print below look at this JJ

dot so what dot dozen vim is it repeats

the previous editing command that was

made and so this is a really nice way of

doing repetitive tasks without typing

the same thing over and over again so in

that particular case that inserted comma

end quote and so it applied the same

thing on this line when I press dot and

then when I guess one final part of this

demo is

we will fix the issue that this program

maybe should take a command-line

argument instead of having this

hard-coded 10 down here so how do we do

that I'll press GG to go to the top

capital o so now I've opened a line

above and I'm going to type in some text

like imports this enter escape to go

back to normal mode and then I want to

go down to where this 10 is so slash 10

makes me jump straight down there CI

pren to edit what's inside the

parentheses and now I can type in like

whatever thing I need to type in here

and then once I've done this my program

does fizzbuzz correctly I think I missed

one change I wanted to make but it

doesn't matter this demonstrates that

you can make lots of changes really fast

so any questions about this demo or the

overall idea we've been talking about ok

so this will be covered Tuesday so the

kind of outside environment I'm running

vim on the left and my shell on the

right and then this is team ox on the

outside one variant of that question

might be like how do you switch between

different vim windows and you can see

the lecture notes for that but there's a

key binding for that so if you have the

same window open or multiple things open

there's a way of doing that question ah

good question so delete takes a motion

and then removes those contents but

keeps you in normal mode so you can keep

just moving around in a file what change

does is very similar to delete it takes

motions and treats them in the same way

deletes those contents but then puts you

in insert mode and so it saves you from

typing one extra keystroke so if I'm

here for example I want to delete main

DW deletes a word but now if I press

whatever key likes I press J it just

moved me down if I undo that do cw4

change a word now it's actually put me

into insert mode and I can type in

whatever I want it to insert so DWI is

the same thing as CW but it saves a

keystroke one thing we've linked in the

resources is something called vim golf

basically people have set up a game

online where you can get an editing task

and try to figure out the minimal number

of keystrokes necessary to complete that

editing

it's actually really addictive so I'd

only suggest going on their chest and

script time I think I saw a hand for

another question yeah uh period yeah one

of the most useful of em commands good

question any other questions

cool so I think we have about five

minutes left and I'm gonna briefly talk

about a thing that's also covered in

detail in the notes so make sure you

look at the notes for this so vim is a

programmers text editor and so of course

it's highly programmable not only

through its interface that's a

programming language but also a couple

of different ways there's lots of

settings that you can tweak to match

your preferences and you can also

install plugins for them that do all

sorts of useful stuff so the way vim is

configured is through a file on disk

called vim RC and you'll see this is a

common pattern in a lot of shell based

tools there'll be a plain text file that

configures how the Tool Works and so if

I edit this file and it may or may not

exist on your machine yet but I've

downloaded the we've created a kind of

default vim RC for you and linked it on

the course website so you can start with

that one if I do vim tilde slash boom RC

I can see here a bunch of comments and

then particular commands like by default

we want syntax highlighting on and we

want line numbers if we didn't do some

of these things like let me remove the

stuff that sets line numbers if I remove

those configurations and relaunch vim

notice that I no longer have line

numbers on the left but yeah so in short

there's a lot of stuff you can configure

with them we've given you a very basic

configuration that tries to like remove

some of the kind of weird behavior

that's on by default in vim but we don't

really try to enforce too many of our

other opinions on you but of course like

the three of us used them a lot and we

have heavily customized VMR C's so we've

linked to our personal configurations

too if you want to take anything from

that and also like thousands or like

millions of people share their var C's

on github so there's lots of places to

look for inspiration

there's also cool blog posts on this

topic another thing you can do in vim is

you can extend it with plugins that do

all sorts of useful things this lets you

do things like fuzzy file

finding which a lot of text editors come

with by default so you can get like a

pop-up window you can type in a name of

a file or approximately the name of a

file and find it very quickly or there

are things that show you like

visualizations of undo history there are

things that show you like file explorers

things like that so we've linked to a

couple of our favorite plugins on the

course website and so I highly recommend

becoming familiar with how to install a

plug-in because it takes like three

seconds and some of them are really cool

and then finally the last topic I'll

briefly mention before we finish today's

lecture is vim mode and other programs

so turns out that a lot of programmers

we're really excited about VIMS

interface and so they've implemented

similar functionality and other tools

for example like I've configured my

Python repple to run in vim mode so I

can like type in stuff here and if I

press escape now I'm in normal mode in

my Python repple and I can like move

back and forth and like press X here

delete a thing like CW change a word and

do all those good things and it's not

just the Python repple like I have my

terminal behaving this way too so like I

can type in whatever I want here and

like escape and I'm in normal mode I can

go here and like go into visual mode

inside my terminal and like select

blocks of text press tilde to change the

case whatever so we've linked sir like

how exactly you can enable vim mode for

like bash z shell fish a lot of read

line based programs like jupiter

notebook a whole bunch of other things

and if it's not another place you can

probably find it by googling it because

a lot of people like to have this sort

of functionality and if you're really

gonna like commit to learning them I

think it's valuable to enable this sort

of like vim emulation mode in every tool

you use is like one or like make you

learn the tool a lot better and to once

you become good at vim like those skills

will now transfer to all your other

tools you use okay so I think that's it

for our rapid introduction to them

there's some other neat material that we

weren't able to fit in today's lecture

but it's in the lecture notes and then

finally I highly recommend going through

the exercises for today like at least

for me personally I think spending time

learning my text editor has been like

the most beneficial thing out of like

the kinds of things we're teaching in

this class

so yeah that's it for today's lecture

and we'll see you tomorrow

note that we've changed tomorrow's

lecture to data wrangling Thursday and

Tuesday lectures are now switched this

is reflected on the course website in

case anybody was going to come to one

but not the other