Lecture 3: Editors (vim) (2020)

okay bene benvenuti alla terza lezione

del semestre mancante

di CI oggi parleremo

di text editors questo è uno

argomento che mi piace molto e penso che sia

uno dei argomenti più importanti che

insegneremo in questa classe perché come

programmatori spenderete molto del vostro tempo

a modificare testi e programmi

se investe tempo nel rendervi

più efficienti nel farlo, risparmierete

un sacco di tempo probabilmente centinaia di ore

durante il corso della vostra laurea o

durante la vostra cariera lavorativa,

i text editors sono leggermente differenti da

altri programmi che potresti usare per modificare ad esempio

cose come la prosa Inglese perchè

i programmare è differente dal scrivere

una prosa Inglese, quando programmate

spendete molto tempo nel leggere cosa

avevate scritto, spendete molto tempo

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 them 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 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

visuals I 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 colon 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 VIMS

command shell so you give vim commands

here instead of shell commands and

they're 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 your

normal mode I can press escape to go

back from command line mode to normal

mode and I press control C I'm like what

happens the lot of programs this doesn't

quit them so how do I quit vim I can

press colon and then go into command

line mode and then I can type in the

command quit key uit you'll see that I

maybe I should move this over to the

middle or something ceases colon quit

and I press ENTER and it quits bin I can

open him up again there's actually a

short form for this command just : Q and

that'll do the same thing and there a

bunch of other useful commands like this

so some other handy wants 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 oh hey I think I've slightly I

should fix that can you fix the config

actually John never mind that

okay so I 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 colon 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

colon 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 colon 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 : that

was if I want to know what : w does I

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

the documentation on : w or : right 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 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 them albeit somewhat

inefficiently so any questions so far

yeah in the back yeah so the question is

what's the benefit of the nura 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 an 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 HTTP link to

an HD HTTP to 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 VIMS model

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 it's models 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 them

a little bit different than the

programming 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 they're a number of tabs and

each tab has some number of Windows and

then each window has a 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 BIM 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

closed the current window and then when

they're no more open windows then we'll

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 in

the second tab that I'd open 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 answer your question of

what is normal mode actually for this is

another really cool idea in them 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 VIMS normal mode like

VIMS interface itself is a programming

language well 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 them's different movement and

editing commands and things like that

you can talk to them 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 HT Cales 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'll be really

slow we don't have to want to have to

hold down these keys and like wait for a

long time for them 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 bins 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 you're gonna

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 I'm on my

cursors 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 we're 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 reg X carrot yeah exactly it goes

to this - let's talk about some more

movement commands there's a ways to

scroll up and down in a buffer so

control U goes up and control D scroll

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 you there's also

ways to move by the entire buffer so

capital G moves all the way down G G

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 double use word B

as beginning for it is end of word those

all seem pretty logical 0 caret and

dollar kind of inspired from reg X 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 l4

lowest makes sense m4 middle and then h4

highest I guess no 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 to something like I

want to jump to the first oh I can press

F oh and my cursor moves to the first

oh I've like found oh I can do FW and

it'll move to the first W which I think

is right here F C 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 a capital FS find the s that's

before that and then there's a variant

of F for find T for two so I can jump to

O and it jumps like until it's found oh

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 really

compose these commands F and T are

finding two and you can say find a

particular character or jump to a

particular character so those are a

couple of them movement commands so any

questions about those so far so this is

yeah question right yeah okay cool so

those are have been 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 which is the eye 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 this back 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

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 put me into

insert modes and 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 vim is just you for

undo so notice my cursors right here I

do DW it's deleted a word I can move

around and then delete another word

suppose I'm keeps getting in the way

suppose I'm like somewhere in the middle

of a word and I want to delete the end

of a word any guesses for what

combination of keys I'd use for that D

and what de exactly delete 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 see e 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 seek 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 D D that

deletes the line if I press C C that

deletes the given line but puts me in

insert mode so I can replace it with

some other line well cover a couple

other 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 you've

had pressed 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 when 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

you while your normal mode so you for

undo is pretty easy to remember so I

press you a whole bunch of times it's

undone all the changes I've made and

then the opposite of undos of course

redo and the binding for that in vim is

control are all right one other editing

command I'm going to talk about is copy

and paste because oh yes question that's

it 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 you

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

you 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 coffee

because yank like that's the word date

that's the term logic 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 in an effect press P for paste

notice that now these two lines are

identical because I've just pasted a

line below you 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 to 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 point 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 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 so 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

I can take this like Visual Studio code

and flick 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 KK KK it goes

up four times but rather than pressing a

particular key again and again I can use

a count so if I press four J it does J

four times right

thumbs interface is a programming

language if I do four K it moves up four

times if I am here and I press me 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 for

word 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 seven dw7 delete

words and so this is particularly useful

for things like suppose my cursor

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 move

down to this line

okay and then one final category of key

meanings in BIM is something called

modifier 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 8 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 this is a

Lincoln 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 to DW and then I to go

into insert mode like that's one of the

many ways I can make this change and I

can type in whatever other thing I want

you to undo huge undo another way could

have done that is change two words C to

W 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 CI bracket 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 X we didn't

talk about parentheses but if your

cursor is hovering over a different

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 parentheses I can delete the contents

inside these parentheses and so those

are vim modifiers I guess we talked

about I but we didn't talk about a if I

do D a parenthesis 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 VIMS

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

hopefully most of you have heard of

fizzbuzz if not I'll explain it super

briefly this buzz 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 & 5 you print

fizzbuzz and if none of those apply you

just print the number so you should

print like 1 2 fizz for 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