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thank you for the kind introduction hello everyone I'm excited to be here
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and share my work with you today uh I I want to introduce luik GI
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mat introduce
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shortly next L Ki will be held in my hometown Aim so please join us also
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today's presentation is almost almost the same as my talk at Luby Ki this year
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so I hope you can get a feel for it today's main topic is Ry but before
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that let me explain a bit about IRB most of you must have used before
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right thank you Irv stands for interactive Ruby and it is Ruby's
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default Leo Leo stands for read eval print Loop which means you can input
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Ruby code IRB evaluates it and output the result you can learn it using the
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IRB command it is also used as a default label for the ls
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console for example when you learn
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IRB 3
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a when you Irv and type is
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equal L comp the string T that when you present
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the result Will C is displayed if you call a method on
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S and a completion dialog appears by default you can move through the
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suggestion by pressing tab the method documentation is also shown the plump
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display IRB main under the line
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number back to the
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slide IB something we use but do you know how it works in simple term this is
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how it works when you learn the ilb command line starts up display the
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prompt and waits for user input once a Val be called segment is entered it is
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sent to IRB for evaluation and the result is displayed on the
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terminal IRB learns a code analyze it and applies color formatting
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in the image IRB recognize Ruby comp as a string and colors it accordingly IRB
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evaluate the line S equal the count on the second line we input s. ask only
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since s is a string the suggestions include a only a string method the
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component responsible for showing these suggestions is leel type completer if
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LEL type complet is not installed IB handle the suggestions the documentation
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for aski only appears on the light and is generated using
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alook so what does the line handle it manages the display and the handling of
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lines while typing theine is responsible for showing the plum the CLE after
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asking only and the dialog boxes you can think the line as the front end on the
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terminal and IRB as a back both IB and line are default GS in the
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3.3 I am one of the committers for this projects my name is Mari maumi I work at
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St Inc where I develop Le applications my pron of heart this is my first time
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in the US and my first time presenting English so I'm
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thank you for being here and please feel free to come and say hi so let's get
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back to the main topic enhancing Line's features first I'll explain what a
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command line editor like line does of its capabilities next I'll compare line
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with with G read line as one of Line's goal is to maintain compatibility with
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it finally I'll explain the design and implementation of and the feature I
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worked on I hope to share what line aims to achieve and what it can do so what is
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line the line is a command line editor here a command line editor refers to
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software that lears on Terminal emulators and handles user input
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although command line editor isn't a common term um I'm using it here because
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there isn't a generic time for software like G read line example include G read
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line and exit liit the line aims to be compatible with these
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libraries when I say a command line editor handles user input but it might
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be hard to picture so let's take a look at what what happens without a command line editor here are three lines of the
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we code this program display please enter your name which for user input and
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print the the enter name when you press ENT wait
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see so this one
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I this one RV okay U now when we learn
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the program it waits for input so let's try entering my name I mean to type
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Mar IM
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oh but I mistakenly typed
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hard to fix this typo I press the left Al key but instead of uh M the castle a
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strange set of characters appeared this is an an escape sequence representing a
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CLE action I wanted to move the CLE B but didn't work as expected and the
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escape sequence was displayed
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instead let's try using line it's simple to use just require line and use LINE Le
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line similar to how get works the read line method accepts a single line of
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to okay uh test to
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RB use reine
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a and I made my type again this time
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I press the left out key to move back and
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Mari IM to me yeah and I was able to
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successfully to change the castle position and correct the mistake this is
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because the line handles the escape sequence and moves Castle back changing
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the castle position on the terminal isn't automatic in this script the line
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processes the escape sequence received from the terminal and adjust the CLE
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position okay thank
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you uh a command line editor provides a set of operations for editing text like
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moving the castle in tools like Irv or bash the Hing of input key is is done by
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the command line editor not by IRB or bash itself let me introduce some command
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line editors the most widely used one is G read line which using in bash IRB up
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to Ruby 2.6 and GDB there's also a library called edit line which comes
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standard with mest the line has been used in IRB starting from Ruby 2.7 and
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is also used in tools like the deak gem Highline and
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hexia now let's look at the features of G read line a wellknown command line
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editor the first feature is line editing which includes basic operations like
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moving the CLE next is history editing which allows you to navigate through the
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command line history using the the app alow key there's also an old complete
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feature such as pressing the Tab Key in bash complete a file name this is
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provided by lead line lead line also offers editing commands such as pressing
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contrl a to move to the beginning of the line and control e to move to the end
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additionally it supports M macros and various customizations through the the
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input RC file since m l Lin go to be compatible with read lines let's do a
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quick feature comparison the line can can be most of the basic operations that
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g read line can such as line editing history navigation and op completion
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however it still La some Advanced features like editing commands and certain configuration that can be set
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through input Ry which I will explain later from the comparison a line may
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seem like a less capable version version of good read line so let me add that
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there are some powerful to whole features unique to theine P it can be
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display dialogues uh such as completion dialogues second theine supports to
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multi support multiline input including plumps plumps while multi-line input is
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also possible with G read line the line Hing with proms makes it easier to use
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third line is extensible Lu Luby you can customize input line decorations
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dialogues completion suggestions and termination conditions for matal input
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using lby procs the line aims to be compatible with G read line but as shown earlier
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some features are missing this include editing commands key binding for those
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commands and toal options occasionally users report issues about features
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features available in Le line but not in the line showing that these features
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would be appreciated Additionally the line is increasingly expected to be compatible
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with lead line starting from the 3.3 lead line X was removed from the default
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gems so when L line X isn't available require lad line will automatically use
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fine this change solves the issue of insulation problems with lead line
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during be build however users may unknowingly switch their dependency from
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Le line X to theine increasing the need for the line's compatibility
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features the issue where require lead line CA the line can be resolved by
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installing the line X but as a maintainer I hope you user chose the
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line over lead line X I want the line to work seamlessly when users switches from
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when you read line without noticing any difference I also hope that theine
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beames to be to theine becames the prefer choice for users considering
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switches their command line editor for example in Pride a p for supporting the
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line has been marged into the master blunch so to summarize the challenges so
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far line aims for compet ility with read line so more compatibility is desired
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additionally it should work simly when require lead line is used so what
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specific are Miss specific features are missing let's take a closer look at the
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feature gaps between the line and read line by the way has anyone here ever
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written on input RC file please L your hand if you have oh
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10 10 five uh fewer than expected thank
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you input RC is a configuration file both lead line and the line can Le input
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RC RC it is typically loaded from your home directory or from a location
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specified by an environment variable in input RC you can set total of options
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editing key bindings and choose between emox mode or V
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mode lead line and L line have to editing mod Emax mode and VI mode the
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default is Emax mode VI mode has both command command mode and is mode but not
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all VI functions are available only simple commands are implemented to
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switch to VI mode you need to add a setting to your input RC
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file input RC is a file that can be written using syntax like this the first
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line says show mod impr prompt on is a setting to display the current editing
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mode in the prompt the second line set VI command mode string configure the
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string display the front when VI is in command mode the third line follows a similar
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pattern the first line is a Comm is comment it out uh anything after sh is
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ignored as a comment L six starts an if statement you can specify software names
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or modes in these conditions for theine you can use if Ruby or if the line in
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this case it configures control e to execute emox editing mode only when the
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line is used the setting on line 10 applies regardless of conditions by
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default it is set to imox mode so this line are the key binding that switches
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to VI mode when contrl s is pressed in imox mode defa key bindings are set within
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the command line editor for example by default control a moves the
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curle to the beginning of the line in VI mode these are separate key bindings for
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command mode and insert mode while customization is possible through input
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RC there are some setting that don't work with the line to understand which
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features are missing I compared the line to read line to see what configuration
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items are supported as of a 16 2024 nine supports 26% of variables and
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44% of editing commands some configuration items like a like file
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name comption are not supported by the line at all so while the coverage is still
00:17:05.000
slow it will be great to implement the features available in lead line but
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missing in lead line however there are 1001 items including setting and
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commands that have been implemented yet we need to start with the most important
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ones and release them first to help prioritize I analyze input files to
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files push to GitHub to see how frequently these setting are used so I
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look at the usage to see how frequently each of one the
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166 configurable item was set this included items were commented out so it
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may not reflect exact usage numbers additionally for functions with default
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key bindings actual usage is likely higher than the number of matches found
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in found in total 6,600 input RC files were
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examined here is a configuration item with high usage rate the top item
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completion ignor case is a setting that makes Auto completion case incentive it
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was found in 3,700 out of 6,600 files which shows it is quite
00:18:29.039
commonly used other frequently used setting include history search setting
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that make t completion more convenient and basic key bindings configurations on the other hand some
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items have a usage late of zero B out of 6600 indicating there are not used at
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all we use information like usage late the presence of defa key bindings and
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issues raised for line to decide which features to ment recently we've added
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features like undo redo show if ambiguous change to editing mode
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supports for mode conditions in input RC and support for bracketed past mode
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Let's Take a look at the implementation of the and feature to understand how the
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line operates from here we'll dive into thei
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code first let's see what the line does when you input a next we look at what
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happens when control a is pressed finally we'll go through implementing
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the UND command let's start by seeing what
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happens in the line when we laar this simple script it's just a program that
00:19:52.480
requires theine CA theine line and print the result with put
00:20:05.400
but this three are be dis
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program when you input a and press Center a is displayed from this call
00:20:23.120
let's examine how line works
00:20:29.960
simply put line processes input this R initialization waiting for input Hing
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input keys and lendering from here I show C in some of which are simplified
00:20:43.640
versions or included addit explanations during initialization
00:20:50.360
theine sets up various configurable blocks this input RC for configurations
00:20:56.720
and establish that default key bindings after initialization read iio
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waits for key input from standard input from Le iio inet C is eventually
00:21:14.440
called and it weighs for input using iio weight readable when input is available
00:21:21.840
I get bite ites one bite at a time for example if you input the lowercase
00:21:29.360
letter A C will F the number
00:21:34.559
97 the received input is pass to line editor update for characters within seven bits
00:21:42.640
config editing mode get method is used to match the key to the corresponding
00:21:49.840
method for example in Max mode if the key is 97 the default key binding
00:21:57.240
assigns it insert to a then Ed insert is called it enal the
00:22:04.480
key which is a number into a string and pass it into inser text the insert text
00:22:12.120
method update the instance variables that manages the input text the
00:22:17.559
variables per Lines line index and V pointer up update this instance variables place an
00:22:25.400
important Lo within the line before L is an aray that holds the text being
00:22:32.000
intered in the case of multi-line input it contains multi-line multiple
00:22:37.919
elements The Prompt itself not included in this aray line index and by poter
00:22:44.840
represent the CLE position line index is used to calculate the y coordinate of
00:22:51.640
the CLE while bite pointer is used for the the x coordinate for example if the
00:22:59.600
input is if one 2 three and the castle is after the three bu far of lines will
00:23:07.840
contain if one and two and line index will be
00:23:13.480
two with the bu pointer at seven these values are used for
00:23:20.200
lendering and a is displayed on the screen if the end condition is met
00:23:26.120
lendering is completed and the input waiting Loop is exited if not it returns
00:23:32.840
waiting for input up to this point we have successfully input and display the
00:23:38.120
character a next let's use the same script and
00:23:44.120
input the contay command which moves the CLE to the beginning of the
00:23:50.679
line initialization and waiting for input works the same be as before and
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when control a is pressed the key code one is input get method is then used to
00:24:04.520
match the key code to its corresponding method when control a is pressed the key
00:24:11.279
code is one so Ed move to beginning is called e mo to beginning says by pointer
00:24:19.320
which represent the the x coordinate of the CLE position to zero meaning the
00:24:26.039
beginning of the line after this the castle position is recalculated and
00:24:31.159
lered allowing the castle to move the start of the line the areas method
00:24:37.320
defined beginning of line and v z which are commands that can be specified in
00:24:43.720
inut SE although the names def they perform the same action so they group
00:24:50.000
using a
00:24:56.399
SE now let's if met undo although undo was not among the top features earlier
00:25:03.240
it is common function in most basic editors and it's useful to have in G read line pressing controlcore executes
00:25:11.120
undo so we implement it in theine to work similarly with control underscore
00:25:18.080
so what is undo undo is a function that we B previous actions however the way it
00:25:24.559
works very varies between editors in new R line for example it likely Leos
00:25:31.440
continuous key strok within a certain time frame as a single unit for undo
00:25:36.960
this mean if you type ABC and press undo the interior ABC is erased reverting to
00:25:45.440
the state before input in the Z line editor if you type ABC and press and do
00:25:53.320
it reverts to AB since the behavior in read line can be somewh unar the line
00:26:00.200
was implemented with the same approach as this year here is a simplified overview of
00:26:07.320
undo when action is performed it is save to the history conversely when UND is
00:26:15.799
executed one entry is poed from the history it sounds simple now let's
00:26:21.720
implement this in the line current line represents the line currently being edited on line is an LA
00:26:29.760
that manages history let's say a is entered this is added to the current
00:26:36.600
line and the previous line is St As Old Line when you want to undo you need to
00:26:43.919
rever to the state before the current line so the old line data is pushed to
00:26:49.440
pass lines next and B is entered the current line which had a now
00:26:57.120
becomes a the old line keeps the previous state which is a the old line
00:27:03.520
data is installed in path lines now control underscore which is
00:27:09.600
the key bindings for undo is pressed when this happen we want to R
00:27:15.840
from a to a to do this one entry is popped from
00:27:21.840
the end pass lines and apply to Cent line destroing it if undo is press
00:27:27.880
repeat reply an empty string is popped returning to the stage before any
00:27:34.640
input this is how the the and functionary was implemented the pr
00:27:40.519
request can be found 7001 in the in depository so please check it uh if you
00:27:47.039
are interested let's take a quick look at the proart from earlier when controlcore
00:27:54.760
is pressed the key binding Cod and and function in the under function a previous St
00:28:01.760
taken from past line and apply to the current line the last ENT three is pass
00:28:07.799
line is removed when lendering is performed the previous state is
00:28:13.519
displayed completing the under operation successfully let's look at the
00:28:27.120
demo when you type if one 2 3 and Del
00:28:32.720
line to oh H pressing control
00:28:41.320
underscore H undo station destroing line two the under
00:28:48.080
also work correctly in the middle of an inut line and the Cal position returns
00:28:53.720
to where it during the operation with this we've successfully implement it and
00:29:10.000
thank to summarize line is a pure designed to be compatible with G line
00:29:16.799
and Li it for has line editing features and can be extended by L not that even
00:29:23.760
when requiring Le line X the line May sometimes be called if you have any
00:29:29.480
feature requests or bug reports please feel free to reach out on the Luby RI
00:29:37.080
repository and here are the links from the foot notes these are versions Ed for
00:29:42.279
testing in this presentation this concludes my presentation enjoy coding on the command
00:29:48.880
line with line thank you very much
