WEBVTT

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hello

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welcome to readme driven design in Emacs

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by adam aard

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if you're a programmer you're accustomed

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to putting a readme file at the root of

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your project

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and it's usually a markdown file but if

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you use an org

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more an org mode file instead you can

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take advantage of the great features

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that org mode provides including

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literate programming

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which lets you generate your source code

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and markdown documentation dynamically

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I want to walk you through a little bit

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of what this looks like

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when you start a project especially if

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if you use something like github you

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begin with an automatically generated

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readme.md file so just delete that

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and instead create a readme.org file

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starting with an empty org file like you

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see here you can begin

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by recording important information about

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your project goals you can add diagrams

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code snippets to-do lists time tracking

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and much more

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I'm going to drop in some documentation

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that I r that I've written about

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about my project here so you can kind of

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see

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what this would look like

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so as you can see I have a title and a

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description and then a sub section

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as well as some code snippets

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and you can see that orgmo does a great

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job of formatting lists and

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code sections diagrams and so forth

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it's good or it's as good or better than

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markdown

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but when you use it in the Emacs you can

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do a lot more

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for example you can dynamically create

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diagrams using graphviz

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from a text description so if you go to

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this source block here

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and hit control c control c you'll see

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that we generate a

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diagram dynamically you can run

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so you can run these code snippets in

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place and get the results

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to show up inside of your your file

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which is a really powerful paradigm

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but most important most importantly for

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the

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purposes my purpose is here

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orgmo provides you the ability to do

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literate programming

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so take a quick look at this diagram

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that I generated here

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and gives you a quick overview of what I

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mean by literate programming

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and how I'm using it you can see

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that we start with a readme.org file on

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top

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at this point we can do one of two

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things

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tangle or weave tangle is used to

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describe the process of

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generating source code while weave

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is the process of generating

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documentation these are terms that

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donald knuth used

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and he's the one that came up with the

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idea of literate programming

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in the early 1980s

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but this is really all that there is to

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it you just

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who are simply using literate illiterate

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source file

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in this case the readme.org to generate

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the rest of the project

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the rest of the project files basically

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so let's dig in to the details of how

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this works

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and I hope you hopefully you'll see how

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cool this is

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so returning to the file here let's

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assume we have enough documentation now

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that we want to get started

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coding so maybe we'll just start with

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like a hello world

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app just so we can make sure that our

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environment is set up correctly

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so let's get started with a code block

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so I created a little snippet to help me

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add

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a source block for literate programming

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quickly

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and there's not much to it

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but there is some important annotations

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here so there's

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excuse me there's a there's a property

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called tangle

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and that takes a value of a file name

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and then there's also a no web property

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called no export

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and basically

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basically the no export will explain

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that a little bit

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more later um it has has to do with how

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the tangling

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is uh done in the tangle step versus the

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weave step and I'll explain that a

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little bit more but the tangle

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field just simply tells tells uh

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Emacs where it needs to generate the

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main.go file and where it needs to put

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it on the file system

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uh you'll you'll notice that we we're

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going to use go

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that's just the language that I've been

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using

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the most lately uh but

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this programming strategy is language

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agnostic

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you could use any language or any mix

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of languages you could create some files

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in python some files and go

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some files in in lisp or whatever you

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want

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and so but let's

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uh let's create just a little hello

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world

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let's use another snippet here to

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generate

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the basics of a go program

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so I'm just going to print

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hello world

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so that's and then

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let's make it a section in our

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file so now you can see we've got this

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snippet

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um when you have a source block in

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inside of org mode you can easily pop

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into a

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language specific buffer by typing

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control c single quote

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so you can see now I have a a go a

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buffer that's in go mode

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and gives you all the ability to edit

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like you would

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normally if you hit ctrl c

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single quote again then it goes back and

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any changes you

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make would will be updated there but you

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can do quite a bit

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just inside of here too there's quite a

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bit of

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language specific

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functionality just in place and so you

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don't always have to go over to a

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separate buffer

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but it's a it's a nice option sometimes

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but now that you have the code in here

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you're going to want to run it

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but right now it just lives here in this

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documentation

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so you need to get a copy of it into a

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separate file

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and that's the tangle process that you

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you need to follow there so I'm gonna

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drop in a little bit more doc a little

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bit more

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documentation really quick here

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okay all right so just kind of as a

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kind of as a side note I like to follow

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this process uh whenever having whenever

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I have an operation to perform I

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I'd like to document it here with a

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snippet that can be executed in line

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then I don't have to leave org mode and

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I don't have to try to remember what I

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did later so instead of just

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trying to do an operation the first time

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I do something I take the

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take the time to figure out what it is

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and document it and so then it's

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recorded

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and so here we find that to do a tangle

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operation

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you run the command or babel tangled

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which is a

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e-list command so if you hit ctrl c

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ctrl c to run it in place you get the

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result

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of main dot go which basically is

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telling us that

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we've tangled one file called main.go

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and you can see that that's true

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if you go to the file system and you

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look

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so now in uh in our demo directory

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we have a readme.org we have that png

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that we generated but we also have a

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main.go

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and if you if you visit that file you'll

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see that it's just the source code that

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was in our documentation which is

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exactly what we expected and what we

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wanted so that's good

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so if we return to

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to where we are at

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now we're we're at the point where we

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have a file on the file system so now we

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need

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um now we need to build it and to

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run it so let's follow the same

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philosophy where let's document

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these operations that we're going to

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perform

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so I'm dropping in a

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a build instruction section and a run

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instruction section

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so as you can see here we have a little

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a bash source block

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and another batch source block this one

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compiles the go build command is what

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compiles a file and then

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the file that gets generated should be

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called demo

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and uh so we just run it here so if if I

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type control c

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control c we get an empty results block

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when you compile things no news is good

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news

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so it means there's no errors so

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presumably we've created an executable

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that's called demo

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so let's uh

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let's look again at the file system and

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regenerate

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yep and what we have here is a demo

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executable which is exactly what we

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wanted

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so let's go back

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so now we should be able to run it so

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ctrl c ctrl c

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and we get hello world as a result

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which was exactly what we were expecting

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so that's already pretty cool

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you can you can do that much

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um but

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that's really just kind of the tip of

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the iceberg to uh to really

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kind of um

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use the more impressive features of

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literate programming we need to uh

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we need to do a little bit more

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so or at least

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at least really to get the full benefit

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of it then

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we need to do

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add some sections that will cause uh

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Emacs to have to to tangle or assemble

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this

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this file from different pieces so

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imagine that we wanted to take this file

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and maybe kind of templatize it

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so using literature programming syntax

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this angle bracket syntax

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let's say that we want to create an in

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imports section

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in a functions section

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and then maybe just a main section and

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we'll get rid of this

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so now you see we've created something

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that looks a little bit like a

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like a template or a scaffolding or

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outline

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for what what our file is going to be it

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looks a little bit like pseudocode

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and what we're going to have literate

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programming do

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is dynamically insert those things into

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those slots

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so the first thing we need to do

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is so let's create a section

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maybe called say hello so we want

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we want to add some functionality that

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makes our program say hello

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so using a different snippet that I have

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for creating something

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that I call like a literate section

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um basically we create a

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another source block that's almost the

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same as the one for the file but it's

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it just has a few differences so say we

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want to

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drop code into the import section and we

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want it to be in go

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here we use the same noed no web no

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export syntax

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but then we've added this no web refs

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imports

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and this ties that slot

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basically to this reference it tells

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Emacs that when you tangle

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we want to stick whatever's in here in

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that spot

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so you skip the tangle file name section

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because you're not actually creating a

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file name you're

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you're putting information into an

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existing file

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so here we would just add the fmt

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for the imports

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so let's add another section for uh

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functions and let's create a

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let's just create a function called

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say hello that

00:13:30.240 --> 00:13:32.839
doesn't have any arguments no return

00:13:32.839 --> 00:13:34.000
types

00:13:34.000 --> 00:13:35.760
all it does is kind of pretty much the

00:13:35.760 --> 00:13:37.440
same thing as we did before

00:13:37.440 --> 00:13:39.199
just print something but let's just say

00:13:39.199 --> 00:13:41.360
hello

00:13:41.360 --> 00:13:45.760
Emacs comp this time

00:13:45.760 --> 00:13:49.519
okay so now we have a function and now

00:13:49.519 --> 00:13:51.040
the function won't do anything unless we

00:13:51.040 --> 00:13:52.720
invoke it so let's do

00:13:52.720 --> 00:13:56.000
one last literate section

00:13:56.000 --> 00:13:59.920
called main make that go

00:13:59.920 --> 00:14:03.519
source block and then let's

00:14:03.519 --> 00:14:06.560
just invoke

00:14:06.560 --> 00:14:10.320
that that function

00:14:10.320 --> 00:14:13.360
so now you can see that we've got

00:14:13.360 --> 00:14:15.600
our scaffolding scaffolding kind of

00:14:15.600 --> 00:14:17.199
outline and then we have

00:14:17.199 --> 00:14:20.079
the sections that we want to get tangled

00:14:20.079 --> 00:14:21.360
or inserted

00:14:21.360 --> 00:14:25.440
so I I've kind of used this syntax

00:14:25.440 --> 00:14:27.199
it's it's kind of borrowed from

00:14:27.199 --> 00:14:28.560
literature programming a little bit with

00:14:28.560 --> 00:14:30.320
a plus equals so really it's just saying

00:14:30.320 --> 00:14:32.480
that I want to append

00:14:32.480 --> 00:14:35.760
this item into the import section so

00:14:35.760 --> 00:14:37.600
it's really just to make a little bit

00:14:37.600 --> 00:14:39.839
more clear what's going on

00:14:39.839 --> 00:14:41.519
when you generate documentation you

00:14:41.519 --> 00:14:43.519
won't see these

00:14:43.519 --> 00:14:46.160
these these particular property

00:14:46.160 --> 00:14:49.360
annotations and so you won't know

00:14:49.360 --> 00:14:51.440
immediately that this section goes in

00:14:51.440 --> 00:14:53.839
the imports area and so I usually put

00:14:53.839 --> 00:14:55.440
a little bit of documentation on top

00:14:55.440 --> 00:14:57.760
there so that it's easy to see

00:14:57.760 --> 00:15:01.120
and you would probably if this was very

00:15:01.120 --> 00:15:03.040
complicated you'd put some

00:15:03.040 --> 00:15:06.399
documentation above to explain what you

00:15:06.399 --> 00:15:07.360
were doing

00:15:07.360 --> 00:15:11.519
maybe right here

00:15:11.519 --> 00:15:13.279
you could you could picture yourself

00:15:13.279 --> 00:15:15.040
maybe explaining

00:15:15.040 --> 00:15:17.440
a complicated algorithm or something up

00:15:17.440 --> 00:15:18.079
here

00:15:18.079 --> 00:15:21.120
and having a nice way to document it

00:15:21.120 --> 00:15:22.959
so now that we've got that here in the

00:15:22.959 --> 00:15:25.600
documentation we need to figure out

00:15:25.600 --> 00:15:27.040
we need to make sure that it's going to

00:15:27.040 --> 00:15:29.920
tangle properly so your best friend

00:15:29.920 --> 00:15:33.519
at this point is is uh

00:15:33.519 --> 00:15:35.680
is a keyboard shortcut that lets you

00:15:35.680 --> 00:15:38.240
preview the tangled operation so if you

00:15:38.240 --> 00:15:38.959
say control

00:15:38.959 --> 00:15:42.560
c control v control v

00:15:42.560 --> 00:15:45.120
it will create a new buffer with the

00:15:45.120 --> 00:15:46.480
tangled

00:15:46.480 --> 00:15:49.360
contents and so you can see here that

00:15:49.360 --> 00:15:50.639
the fmt

00:15:50.639 --> 00:15:53.199
import went to the right place that

00:15:53.199 --> 00:15:54.720
function went to the right place the

00:15:54.720 --> 00:15:56.160
function invocation went to the right

00:15:56.160 --> 00:15:58.480
place and so we're feeling good

00:15:58.480 --> 00:16:01.279
you can nest these things many layers

00:16:01.279 --> 00:16:02.800
deep

00:16:02.800 --> 00:16:04.800
actually so like if you came into the

00:16:04.800 --> 00:16:07.199
say hello function you could add

00:16:07.199 --> 00:16:10.560
more sections

00:16:10.560 --> 00:16:12.160
you know and it gets and it'll go

00:16:12.160 --> 00:16:13.759
through and it'll

00:16:13.759 --> 00:16:15.680
keep track of all that and tangle it for

00:16:15.680 --> 00:16:16.959
you so you really get a lot of freedom

00:16:16.959 --> 00:16:18.320
and flexibility for how you want to

00:16:18.320 --> 00:16:19.600
document things

00:16:19.600 --> 00:16:22.320
by doing this so now that we've

00:16:22.320 --> 00:16:25.839
previewed it and we feel good about it

00:16:25.839 --> 00:16:28.639
we need to uh we need to tangle so we

00:16:28.639 --> 00:16:31.440
get the file on the file system

00:16:31.440 --> 00:16:34.480
so ctrl c ctrl c and

00:16:34.480 --> 00:16:37.199
get just main.go comes back again

00:16:37.199 --> 00:16:37.920
control c

00:16:37.920 --> 00:16:40.959
control c and no errors come back

00:16:40.959 --> 00:16:43.839
and then if we did this right when we

00:16:43.839 --> 00:16:45.600
when we run this we should get hello

00:16:45.600 --> 00:16:47.199
Emacs comp so ctrl c

00:16:47.199 --> 00:16:51.199
ctrl c hello Emacs comp

00:16:51.199 --> 00:16:54.800
so I uh

00:16:54.800 --> 00:16:57.120
I think that's pretty pretty cool

00:16:57.120 --> 00:16:58.240
actually so we've got

00:16:58.240 --> 00:17:00.160
kind of the breadcrumbs of the process

00:17:00.160 --> 00:17:02.399
we've gone through to get to this point

00:17:02.399 --> 00:17:05.520
this initial this initial

00:17:05.520 --> 00:17:08.000
document that has some tangling in it we

00:17:08.000 --> 00:17:09.919
have documentation for how to tangle

00:17:09.919 --> 00:17:12.799
how to build how to run it's we've

00:17:12.799 --> 00:17:14.079
really built a nice

00:17:14.079 --> 00:17:17.760
foundation for

00:17:17.760 --> 00:17:20.160
moving forward on our project and a nice

00:17:20.160 --> 00:17:21.439
way of breaking things out and

00:17:21.439 --> 00:17:23.280
documenting further

00:17:23.280 --> 00:17:27.120
the last piece that we need to

00:17:27.120 --> 00:17:30.559
take care of is the weave that I

00:17:30.559 --> 00:17:34.799
that's I showed you in the diagram above

00:17:34.799 --> 00:17:38.640
so one more time we'll drop in

00:17:38.640 --> 00:17:41.760
some documentation so this time on how

00:17:41.760 --> 00:17:42.400
to weave

00:17:42.400 --> 00:17:44.400
so it's really just an export function

00:17:44.400 --> 00:17:47.520
it's not there's not a separate weave

00:17:47.520 --> 00:17:49.280
command going on here we're just going

00:17:49.280 --> 00:17:50.640
to export

00:17:50.640 --> 00:17:52.799
what we've got here into a markdown

00:17:52.799 --> 00:17:55.200
format so we're using org

00:17:55.200 --> 00:17:57.440
gfm export to markdown which is the

00:17:57.440 --> 00:17:58.880
github style

00:17:58.880 --> 00:18:02.160
markdown you can use the other just

00:18:02.160 --> 00:18:05.440
more standard type as well so hit ctrl c

00:18:05.440 --> 00:18:10.320
ctrl c now you see we've got a readme

00:18:10.320 --> 00:18:15.280
file and if you look

00:18:15.280 --> 00:18:17.440
in the file system we've got that right

00:18:17.440 --> 00:18:19.120
there and so

00:18:19.120 --> 00:18:23.120
if you go to something like ghostwriter

00:18:23.120 --> 00:18:31.679
and open that file

00:18:31.679 --> 00:18:34.559
now you can see that it's generated some

00:18:34.559 --> 00:18:35.520
documentation

00:18:35.520 --> 00:18:38.320
it puts a index at top at the top I

00:18:38.320 --> 00:18:39.679
usually just

00:18:39.679 --> 00:18:42.000
I usually turn that off it's easy to do

00:18:42.000 --> 00:18:43.679
that by putting a property at the top of

00:18:43.679 --> 00:18:44.559
your

00:18:44.559 --> 00:18:46.880
your org file but some people like to

00:18:46.880 --> 00:18:48.559
have an index

00:18:48.559 --> 00:18:50.799
but here you can see that it's generated

00:18:50.799 --> 00:18:52.160
pretty nicely and

00:18:52.160 --> 00:18:55.200
formatted snippets well

00:18:55.200 --> 00:18:56.880
put the diagram in there and then it's

00:18:56.880 --> 00:18:58.240
preserved

00:18:58.240 --> 00:19:01.039
it's preserved this literate programming

00:19:01.039 --> 00:19:02.799
syntax

00:19:02.799 --> 00:19:04.960
which is important because that's how we

00:19:04.960 --> 00:19:06.480
want to view the documentation that's

00:19:06.480 --> 00:19:07.200
what the no

00:19:07.200 --> 00:19:10.559
exports um

00:19:10.559 --> 00:19:13.360
property was was trying to maintain so

00:19:13.360 --> 00:19:14.000
that

00:19:14.000 --> 00:19:16.080
no exports means when you export do not

00:19:16.080 --> 00:19:18.400
try to tangle so that's

00:19:18.400 --> 00:19:20.559
hopefully that makes more sense now but

00:19:20.559 --> 00:19:22.240
now you can see all the documentation

00:19:22.240 --> 00:19:26.080
and I think it demonstrates a

00:19:26.080 --> 00:19:29.919
pretty useful feature that's inside of

00:19:29.919 --> 00:19:33.520
Emacs and and hopefully

00:19:33.520 --> 00:19:35.039
hopefully you'll have as much fun using

00:19:35.039 --> 00:19:39.919
that as I have

00:19:39.919 --> 00:19:43.600
so thanks