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How I fixed a bug in Atom

davidvgalbraith.com

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Re: How I fixed a bug in Atom

#51

Post by TazeTSchnitzel »

viraptor wrote: post #17
boulos wrote: post #11

I got to the bottom and couldn't believe that the solution chosen was to modify the regexp instead of use a for loop. He did such a great job explaining that the code is really just trying to count the number of parentheses or braces to see if they're imbalanced, that it felt the next step was "so I wrote a really simple set of loops that is fast enough on short strings and way less crazy otherwise".

Same here. Also, I don't use Atom, but looking at the expression I'm pretty sure it fails to account for strings with parentheses. The way the matching is done, it looks like it will happily count: func("some call :)") as extra closing paren. (regex101 agrees)

This could be solved by using regexes to tokenise instead, then detecting brackets. Tokenising is something regular expressions can actually do well. Directly parsing source code is not.

Re: How I fixed a bug in Atom

#52

Post by lorenzhs »

wfunction wrote: post #20
cyphar wrote: post #10

First of all, this is why people should stop adding stupid features to regular expressions. A sane regular expression implementation has no pathological cases. DFA generation can be done in O(n^2) from memory (in the absolute worst case O(n) is average), and matching can't be worse than O(m) or similar (n is the size of the regex and m the size of the string). When you add features like back references and recursive…

> The conversion from DFA to NFA [...] I believe you mean NFA to DFA. > [...] would require O(n^2) in that case I believe you mean O(2^n). https://en.wikipedia.org/wiki/Powerset_construction#Complexi...

Fun with automata: Constructing the minimal DFA for a given NFA is PSPACE-hard. There are families of NFAs with n states so that the powerset automaton has 2^n states, but the minimal DFA has 1 state. Example: Let Σ={a,b} be the alphabet, Q={q1, ..., qn} be the states. q1 has a self-loop with both a and b and a transition to q2 with a. q2 to q(n-1) have transitions with a and b to the next state (q2 -> q3 etc). qn has no transitions. q1 and qn are the only accepting states. This is basically the "n-th-to-last letter was an a" automaton with the modification that the starting state is accepting.

Re: How I fixed a bug in Atom

#53

Post by andrewingram »

Lazare wrote: post #44
josteink wrote: post #40

Completely unrelated to the issue at hand... I had no idea Atom was written in CoffeeScript. I thought it was written in Javascript, which made me positive at the thought of hacking into it. But this code? Definitely giving me a headache, and my interest went down to zero. There seems to be a meme and unchallenged claim in hacker circles that CoffeeScript is somehow more "readable" and easier to understand. Allow me…

First, good news: The Atom teams is (slowly) moving away from Coffeescript towards modern JS, and I think they'd agree (unofficially) that the choice proved to be a mistake. Beyond that... 1. The JS world moves stupidly fast, and Coffeescript is a relic of a now-vanished age. It was born, it evolved, and it died. Back in those long ago days of, um, 5 year years ago, there was no ES6, and Coffeescript looked a lot mor…

In fairness, I built a fairly large app using CoffeeScript and it still took a lot of brainpower to read it compared to JS. All the typical complaints about ambiguous-looking syntax match my experiences exactly.

I ended up with a general workflow of having my Coffeescript source and the generated JavaScript sitting side-by-side so I could check that the output was what I was expecting. I've only had the urge to do that with ES6 and Babel a couple of times.

Re: How I fixed a bug in Atom

#54

Post by Kristine1975 »

EdiX wrote: post #22
wereHamster wrote: post #7

Could be avoided if the editor had a full AST of the code instead of using regular expressions to try to make sense of it.

The syntax will be broken 99% of the time and making a parser that recovers gracefully under any circumstance is very hard. You could make an editor that only allows valid programs but that opens up a lot of UI problems, it was tried many times and it never took off in practice.

Yet Eclipse and IntelliJ IDEA (and most likely a lot of other IDE's) successfully use AST's for their code editor. The syntax will only be broken locally, so it's not that hard to recover.

Re: How I fixed a bug in Atom

#55

Post by TazeTSchnitzel »

josteink wrote: post #40

Completely unrelated to the issue at hand... I had no idea Atom was written in CoffeeScript. I thought it was written in Javascript, which made me positive at the thought of hacking into it. But this code? Definitely giving me a headache, and my interest went down to zero. There seems to be a meme and unchallenged claim in hacker circles that CoffeeScript is somehow more "readable" and easier to understand. Allow me…

CoffeeScript is supposed to be this nice Ruby/Python-esque sugar for JS. It does resemble those languages, but it's not nice, it's very... stabby. Indentation is unintuitive and makes code do completely different things (whereas in Python it just delimits blocks, and if you get it wrong the compiler will moan at you). Functions implicitly return the last value they produce. You can omit brackets in function calls - but only if there's arguments, otherwise you've accidentally made a NOP.

It's horrible. It's a nice idea, but the implementation leaves so much to be desired. It's bitten me before and so I avoid it now.

Re: How I fixed a bug in Atom

#57

Post by scotty79 »

josteink wrote: post #40

Completely unrelated to the issue at hand... I had no idea Atom was written in CoffeeScript. I thought it was written in Javascript, which made me positive at the thought of hacking into it. But this code? Definitely giving me a headache, and my interest went down to zero. There seems to be a meme and unchallenged claim in hacker circles that CoffeeScript is somehow more "readable" and easier to understand. Allow me…

If you can't read CoffeeScript then just compile it to JS. Result is more readable than most people produce in JS by hand.

For me CoffeeScript is just shorthand syntax for well structured, fast JS although I agree that ES6 is good CoffeeScript replacement (destructuring FTW) if you can suffer through braces, colons and `function` keyword.

TypeScript is all the rage today.

Re: How I fixed a bug in Atom

#58

Post by ousta »

Performance wise I never understood why ATOM is even used. it is lackluster compared to a notepad++ and there is a delay in every action: loading the software, clicking on a tab, on a menu, on an option. it seems to me like a very wrong idea to push the web into softwares

Re: How I fixed a bug in Atom

#59

Post by anotheryou »

Lazare wrote: post #45
viraptor wrote: post #17

Earlier quoted context omitted.

Same here. Also, I don't use Atom, but looking at the expression I'm pretty sure it fails to account for strings with parentheses. The way the matching is done, it looks like it will happily count: func("some call :)") as extra closing paren. (regex101 agrees)

Sometimes I feel like the difference between a junior, intermediate, and senior developers is that the junior hasn't yet figured out how to use regexps, the intermediate dev has, and the senior dev has figured out not to. I kid, but...really. The number of times I've seen people burnt by non-trivial regexps in production code is absurd. "Oh, I need to mangle this CSV that's in the wrong format"? Sure, write a one-off…

out of curiosity: what would you use for the URL validation?

(but i get this is difficult: https://gist.github.com/dperini/729294 )

Re: How I fixed a bug in Atom

#60

Post by davej »

josteink wrote: post #40

Completely unrelated to the issue at hand... I had no idea Atom was written in CoffeeScript. I thought it was written in Javascript, which made me positive at the thought of hacking into it. But this code? Definitely giving me a headache, and my interest went down to zero. There seems to be a meme and unchallenged claim in hacker circles that CoffeeScript is somehow more "readable" and easier to understand. Allow me…

The semantics are the same (with a couple of minor exceptions) as Javascript so it's just sugar really. I found it very easy to reason about, it often comes down to whether or not you are comfortable with reading significant whitespace.

I liked CoffeeScript but haven't used it in years. IMO CoffeeScript is probably a bad choice for a modern dev environment.

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