Engineering lead for @typescript. Now at bsky.app/profile/searyanc.deβ¦
Seattle, WA
- Tweets 8,325
- Following 383
- Followers 8,507
- Likes 5,437
Trying out Twitter 2: The Twittening. Follow @ bsky.app/profile/searyanc.deβ¦
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"Do senior devs still have to look up stuff on StackOverflow?"
Gentle reader, I have gone to StackOverflow to read answers that I wrote about behavior that I myself designed and implemented.
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"X is a compiler" alignment chart
ALT Input must be a program + Output must be binary = gcc is a compiler Input must be a program + Output must be instructions = prettier is a compiler "Input must be a program + Output can be anything = An orchestra is a compiler" "Input must be text + Output must be binary = Microsoft Word is a compiler" Input must be text + Output must be instructions = Javadoc is a compiler "Input must be text + Output can be anything = AI Dungeon is a compiler" "Input can be anything + Output must be binary = A coin flip is a compiler" Input can be anything + Output must be instructions = Bop It! is a compiler "Input can be anything + Output can be anything = The sun is a compiler"
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I'm excited to stop writing code and start writing machine-readable specifications of precise intended behavior
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JavaScript performance is bananas, a thread.
Let's write a function to sum the values from a the 'val' property of each element in an array:
function sum(arr) {
let acc = 0;
for (let i = 0; i < arr.length; i++) {
acc += arr[i].val;
}
return acc;
}
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"I can't believe *none* of the things I'm trying are working here" - guy who keeps running a different file than the one he is editing
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"Not sure why you don't have this yet. It's very simple code; I'll send a PR"
ALT Iceberg Above water: writing the code Below water: * testing it on all platforms * interaction with other configuration * performance * security * documentation * localization * interaction with future features
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Us: Can barely get usefully stable perf numbers from our CI machine
Other people: Doing timing attacks on the branch predictor from JavaScript code
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Today someone told me that String#split can NEVER return an empty array, which is wrong, but I can see how one might arrive at that conclusion. Every day I learn something worse about JavaScript
![> "".split("")
[]
> "".split(" ")
[""]](/pic/orig/media%2FEnr-KnWVEAAW_FH.png)
ALT > "".split("") [] > "".split(" ") [""]
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If "Do you *really* know JS?" quizzes were applied to other domains:
* What's the towing capacity of an ambulance?
* Will putting 600 kV backwards through a standard LED cause an explosion, a fire, or both?
* T / F: pine sawdust tastes worse in a martini than oak sawdust
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My wife used to work on the caching team at Amazon and every few months someone would pop in to say "I wrote a simple cache (with no eviction policy yet) and it's 30x faster than memcached when pulling on the same key 50,000 times in a row, maybe you can use it instead?"
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Telling someone you're vaccinated? HIPAA violation. Straight to jail.
Asking someone how their day is going? HIPAA violation.
Wishing someone a happy birthday on Facebook when you only know it's their birthday because Facebook told you? Believe it or not, HIPAA violation.
ALT Fred Armisen in Parks & Rec
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JKR 5 days ago: There's a single immutable unambiguous biological definition of who is a man
JKR today: Man is when man vibes
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C++ still doesn't have automatic garbage collection after like 30 years. I guess the devs just don't care. Anyone know where I can send a PR to fix it?
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TypeScript: *powers JavaScript JSDoc-based Intellisense in VS family; gets better every release*
JS Devs: "Wow, JS Intellisense is so good these days you hardly even need TypeScript at all"
TypeScript:
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If you say a 10x engineer's name backwards, they will owe you three wishes. One of them will backfire terribly
10x engineers
Founders if you ever come across this rare breed of engineers, grab them. If you have a 10x engineer as part of your first few engineers, you increase the odds of your startup success significantly.
OK, here is a tough question.
How do you spot a 10x engineer?
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C#: No abstract static methods
C++: No abstract static methods
Java: No abstract static methods
Swift: No abstract static methods
Obj.C: No abstract static methods
Ruby: No abstract static methods
Devs on GitHub: Why is TypeScript still missing abstract static methods? Sad.
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Got a PR from a bot to make the following changes
* hello -> theyllo
* cowboy -> cowchild
* this -> ttheir
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Love the approach
ALT "Guy getting thrown out a window" meme > We need this to run faster > rewrite in rust > rewrite in zig > use basic caching and work-skipping
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STOP DOING JAVASCRIPT STRING ITERATION
ALT STOP DOING JS STRING ITERATION YOU CAN'T ITERATE ANY OTHER PRIMITIVE Are you trying to break apart combined emoji like π©βπ©βπ§βπ¦ for Twitter likes? We've seen it already, stop trying to steal Kyle Simpson's bit YEARS of LOOKING but NO ONE has found a "ZERO WIDTH JOINER" key on their keyboard Wanted to fail on non-ASCII inputs? We have that already it's called charAt "DO YOU MEAN A GRAPHEME, CODEPOINT, SURROGATE PAIR, UTF-32 WORD, OR GLYPH?" - Statement dreamed up by a Completely Deranged Unicode expert Literally no one knows what's supposed to happen in ideographic or RTL languages LOOK what actual string iteration has given us for loops DON'T EVEN WORK .length tells you NOTHING "Hello I would like a string of length 11 that iterates into 7 elements" - actual programmers who don't realize their code is about to crash They have played us for absolute fools
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If you find two 10x engineers engaged in an argument, you're in for quite a sight. They will argue until one is declared victor, who will entirely devour the other, gaining the defeated engineer's stock options in the process.
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People will really stay in the same location all day tapping at their keyboards then say they don't like static typing
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I spend all day every day telling people on GitHub that we're not doing features because it'd infringe on the TC39 committee's areas of ownership. "Taking over an open standard" is completely the opposite of what's happening. 1/?
Microsoft is smart enough to know that a huge body of developers still remember how it behaved in the 90s and so it puts in lots of effort to avoid appearing to take over an open standard and replace it but, well, that's what's happening.
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Excuse me Mr Astronomer but according to this star registry certificate I bought on SkyMall, this star is mine
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JS perf is extremely hard to reason about: algorithmic improvements that halve the number of calls to a function can still be worse on net if those calls make the function megamorphic. Code that runs "fast" now might run "slow" later if other inputs go through that codepath 9/10
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lol
![> new Date(32, 10, 4)
Fri Nov 04 1932 00:00:00 GMT-0800
> new Date([32, 10, 4])
Mon Oct 04 2032 00:00:00 GMT-0700](/pic/orig/media%2FE38ERh8UUAI89Mm.png)
ALT > new Date(32, 10, 4) Fri Nov 04 1932 00:00:00 GMT-0800 > new Date([32, 10, 4]) Mon Oct 04 2032 00:00:00 GMT-0700
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Avoiding polymorphic calls is another thread entirely, but the takeaway I want you to get is taht moreso than in other systems, you need to measure measure measure measure, and make sure your measurements are as near as possible to the real thing you're trying to build. 10/10
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BlackRock should open up a flailing candle shop in every suburban strip mall just to be sporting
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I feel like signing a contract that stipulates a late fee while simultaneously responding to these messages with "we don't pay late fees" is tantamount to fraud
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Humblebrag: Today I was accused of overestimating the complexity of a software feature, a feat previously unaccomplished in the history of our industry
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If it's a fixed object then it's not in a vehicle's path. You're talking about out of control vehicles.
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Let's dig in. Gary's discovery is thankfully easy to reproduce
let b: 1 | 2 = 3;
This indeed produces the error (under --target ES5)
Type '3' is not assignable to type '1 | 2'.
and with --target ES6:
Type '3' is not assignable to type '2 | 1'.
Cool, what the heck?
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Multiple replies pointing out this example is V8 behavior (true ty), but all fast JS interpreters have unintuitive performance characteristics in some cases. The point is, measure measure measure, using the realest benchmark you can. Never say "this *should* be faster", measure!
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Advanced #TypeScript concepts: Study and memorize the type alignment chart
![Alignment chart. Rows in order Lawful, Neutral, Chaotic
Good: string, object, void
Neutral: any, unknown, this
Evil: Object with capital O, {}, []](/pic/orig/media%2FEJwkNs6UUAANhib.png)
ALT Alignment chart. Rows in order Lawful, Neutral, Chaotic Good: string, object, void Neutral: any, unknown, this Evil: Object with capital O, {}, []
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Me, writing a webpage for cat pictures:
* Is the result in the server's L3 cache?
* Will the user's ambient lighting affect perceived color temperature?
* Is latency harmed by Nagle's algorithm?
* Will showing these cats badly impact democracy?
* How to center this div??
100% there should be no such thing as a front end developer outside of super junior contexts. All developers need to think across all the layers that they build on to be effective.
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Where were you when you found out Optional Chaining went to stage 3?
ππππBREAKING: #TC39: Optional Chaining has now moved to Stage 3!!!
#JavaScript
ALT Optional Chaining Example found on https://babeljs.io/docs/en/next/babel-plugin-proposal-optional-chaining.html
ALT Optional Chaining Example found on https://babeljs.io/docs/en/next/babel-plugin-proposal-optional-chaining.html
ALT Optional Chaining Example found on https://babeljs.io/docs/en/next/babel-plugin-proposal-optional-chaining.html
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Here's one way to think about this.
Would you ever intentionally _ship_ unminified JS to your production website? Probably not
Do you _write_ minified code today? Definitely not.
But is it useful to be able to _run_ unminified code? Extremely!
Could we have TypeScript with no build step? Could we have types in JavaScript? Maybe!
We're exploring bringing optional type syntax into the JavaScript language!
devblogs.microsoft.com/typesβ¦
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An eagle-eyed user spotted that the color used for TypeScript in the GitHub Languages repo breakdown wasn't the same shade of blue as used in our official branding.
As of today, that's fixed. Happy Friday! #3178c6
![Languages
[a blue bar that is the official TypeScript blue]
TypeScript 100.0%](/pic/orig/media%2FFU6m-6SUAAAT1IJ.png)
ALT Languages [a blue bar that is the official TypeScript blue] TypeScript 100.0%
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Please, for the love of god, do not abuse this flag. It's not here for aesthetic reasons to let you write paths that are actually misleading.
Turns out I was totally off-base with a post I made last week.
You'll never need to write a `.js` import again, thanks to this new flag in TS 5.7.
The TS team changed their mind. This is massive.
π§΅
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Why does fuddy-duddy TypeScript say I shouldn't pass a number to parseInt? Haven't they read the ES spec? It goes through a coercion process that is totally lossless, probably
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Still a CSS noob because I can't figure out if I should do
body { margin: 6 ft; }
or
body { padding: 6 ft; }
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The weirdest feedback on TypeScript that I see is that the type system is getting "too complex", when in reality we only ever add type system features to support existing behavior of JavaScript libraries
Blame the territory, not the map π
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Sometimes I see conditional types like this:
type F<T> =
T extends "a" ? A :
T extends "b" ? B :
T extends "c" ? C :
(... many more)
never;
When the test type is always a literal or literal-like thing (e.g. unique symbol, enum), this often isn't the best approach 1/
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"No committees"
...
"Who's responsible for these changes? David and I are. Who made the changes? David and I did. These are our calls, and the outcomes and impacts land at our doorstep."
If only there were a name for a decision-making group like the one Jason and David comprise
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If a 10x engineer becomes bored with the product, they'll often embark on a spiritual quest of refactoring. If this succeeds, you will notice absolutely nothing. If this fails, the 10x engineer ascends to become an Architect, and you'll have to double their pay for no reason.
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When sum hit the different objects at the end of the array, they were not the same shape as the rest, so the property access became "megamorphic" - not suitable for optimization.
See also erdem.pl/2019/08/v-8-functioβ¦
But array1 is still fine, right? 6/10
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That's what working with the process looks like - we waited over 5 years (an eternity in JS tooling years) before adding our most-wanted feature because we're *not* taking over an open standard.
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It turns out the answer to "What if we made query parameterization as convenient as string interpolation?" is "People assert that it's vulnerable to injection, regardless of how it works"
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Last Thursday, the @typescriptlang npm package had a million daily downloads for the first time ever
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We call sum(array1) five times again and measure the time in milliseconds:
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Now array1's performance is as bad as array2's was in its final run. sum is permanently megamorphic and much slower now. 7/10
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TypeScript came in #3 (tied for #2?) for Most-Loved in the StackOverflow Developer Survey this year. We β₯ you too!
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The Netlify docs claim to already have DDoS protection. Why shouldn't customers expect that they're protected against outrageous charges from DDoS attacks?
ALT Support against DDoS attacks Even if a malicious attacker tries to take down your site, our global infrastructure and automated DDoS protection can keep your site available. Netlify automatically detects distributed denial-of-service (DDoS) attacks and will rate limit and block malicious clients from connecting to sites hosted on our servers.
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Incompleteness is when your program works, but the computer doesn't believe you. This is a necessary part of all type checkers due to Math (see GΓΆdel, 1931), and also often for performance reasons
A common source of incompleteness in TypeScript is ... π§΅
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PSA: Due to Brexit, the U.K. will be switching back to 7-bit bytes at the end of the year. Please ensure your systems are updated.
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I was thinking about blogging but then I remembered I'm not done writing my own static site generator yet.
Don't laugh this is not a joke
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Ah yes, AirBnB, a famously not-TypeScript company github.com/airbnb/ts-migrate
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TypeScript: *has over a dozen commandline flags for controlling typechecking behavior*
TC39: *can't decide on exact syntax of obj?.prop; proposal is blocked for several years as a result*
People: "Browsers will definitely have built-in type checking any day now"
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The C compiler was an artificial intelligence system that used deep learning to automatically allocate registers and produce bytecode, allowing true "no code" development using a special DSL to describe the desired behavior of the output program
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Anyone voting True on this would get 70% of the way through writing a new layout engine, find out that RTL exists, and throw away their computers to go live in the woods foraging for berries.
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Just a normal JavaScript thing. What's the value of 's' ?
ALT > typeof s "string" > +s 10 > parseInt(s) 10 > parseInt(s, s) 0
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The TypeScript team is looking to hire a Senior Software Engineer! Do you have expertise and interest in areas like developer tools, compilers, Node.js, and (of course) TS/JS?
Apply now at careers.microsoft.com/us/en/β¦
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Even families making $800k are left with nothing after accounting for taxes, spending, and saving
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Really loving how every reply to a reply on this thread is people mansplaining JS incorrectly
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I was excited for the discourse to reach the "Adding comments to JavaScript was a mistake actually" point and now here we are
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People: They should close tax loopholes
Also people: Totally gutted they're stopping the Mega Backdoor Double Secret Probation After-Tax Roth 4IRA01k Fliptober method
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This headset works, but it's got a lot of problems. What can we do?
v1: People keep getting motion sick. Remove the head-tracking thing and let people adjust the camera manually
I want a TikTok sketch where two engineers are trying to create the perfect AR headset and incrementally make a normal flatscreen monitor
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A small announcement - @fdsmars (mhegazy on GitHub) is moving on to new adventures and I'll be taking over as interim engineering lead on @typescriptlang. My short-term goals are to not ruin anything and keep this awesome type train on the tracks! πππ
Best of luck Mohamed!
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This coal plant emits less CO2 than all humans' breathing combined, so it's basically green energy
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Every time someone inappropriately cites this page, @drosenwasser adds another h1 warning at the top
github.com/Microsoft/TypeScrβ¦
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When TypeScript was released, CoffeeScript was 3 years old and soon to be on the decline. TypeScript is going to turn 7 this year. We're long past the point where using one to predict the other's fate is meaningful.
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Microsoft is truly an OSS-first company now: We're having a reply-all storm on the GitHub org 'everyone' channel instead of via email
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Can we not? π
ALT Intellisense tooltip showing 97 additional overloads for a function call
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Sometimes "document the workaround" is the best you can do
ALT A light switch with a label maker label below it reading "LIGHT SWITCH MUST BE ON TO WATCH TV."
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Everyone saying "That isn't a bike lane" please turn in your driver's license and report for a free eye exam
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The Y2K denialism out there today is so strange. You can talk to literally anyone who was working in the industry at the time and they'll tell you about the necessary work that was done.
It isn't difficult to get history right when the people who did the thing are still alive!
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Tech hiring: We'll judge you on ability to implement obscure tree algorithms from the 1980s
Also tech hiring: There's a 7-month gap in your resume, have you been able to keep up on the dozens of important frameworks that have churned in and out of favor in that time?
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Sometimes people suggest adding a feature to TypeScript, and that we can just tell people not to use it in a particular way that would be very problematic, thus rendering the problem moot.
I am here to tell you that no one hears the second part. This isn't a thing that works.
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Today's cursed code snippet is
a ? (x) : b => (c) : d => e
which either means
a ? ((x): b => c) : (d => e)
or
a ? x : (b => ((c): d => e))
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This is despite the fact that every object to ever enter 'sum' had 'val' as its first property with type number, and that sum ever only looked at that property. Doesn't matter; the extra properties are different types and this 100% matters to the engine. 8/10
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People saying they have library behavior that can't be expressed in TS either don't know enough about what TS is capable of, or are shipping some truly galaxy-brained API design that humans are unlikely to be able to understand
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I can't believe these 12 lines don't explicitly demonstrate every layer of a real app architecture. Also, where are the tests? Are they saying you shouldn't write tests? I would have put tests, docs, and a diagram showing the load balancer, all on this one slide, for clarity
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