scala/scala

Discord is now Scala’s main chat platform. Please join us at https://discord.com/invite/scala

Sorixelle

@Sorixelle

Ah, yeah, that does work

Sorry about that, being a little silly :P

kevinwright

@kevinwright

It’s not about whether you need the override - it’s about having the compiler enforce that you’re doing what you thought you were doing

As opposed to just shadowing the name, for example

Sorixelle

@Sorixelle

Yeah, I think I just got a little confused

Just started to pick up shapeless today, and I'm still getting the hang of some of the concepts it employs

Fabio Labella

@SystemFw

yeah that's a common shapeless pattern, e..g Out <: HList

Dominic Egger

@GrafBlutwurst

https://scalafiddle.io/sf/PuO83B1/1 I didn't know that null is such a footgun in that case. Isn't there a way to coerce the compile to block at the x:Qux.Aux[Baz] ?

ahh type Aux[A <: Foo] though it's a bit a bother to have to declare that bound twice

Martijn Hoekstra

@martijnhoekstra

null is such a footgun in all cases

Dominic Egger

@GrafBlutwurst

well. actually I'm more surprise about the aux pattern that you have to do the bounds twice there. or is this another shadowing thing?

kevinwright

@kevinwright

We’ll have a better way in Scala 3 :)

RoelofWobben

@RoelofWobben

oke , and when it that due ? @kevinwright

Sorixelle

@Sorixelle

But yeah, thanks for helping out

kevinwright

@kevinwright

You can start playing with Dotty now

But final release is still some way off :)

RoelofWobben

@RoelofWobben

just doing my first steps so I think its not wise to play with something new

How do I import the list class so I can do this challenge :

We’re going to use Scala’s builtin List class for this exercise as it has a flatMap method

Martijn Hoekstra

@martijnhoekstra

it's imported automagically for you, you don't have to import anything

unless you've disabled that

RoelofWobben

@RoelofWobben

oke

Martijn Hoekstra

@martijnhoekstra

then it's import scala.collection.immutable.List

RoelofWobben

@RoelofWobben

then I have to figure out how to use flatmap

back to the book

Mark Hammons

@markehammons

ok, yesterday I was talking about using sortedset to handle a request queue

Martijn Hoekstra

@martijnhoekstra

yeah, you did. It seemed like a fun problem

Mark Hammons

@markehammons

and now I've revised my design to get the heads of all the queues in children nodes to find the earliest request

Martijn Hoekstra

@martijnhoekstra

though I didn't really understand the exact requirements

Mark Hammons

@markehammons

I have lock requests. The locks can be on files or directories, and they can be recursive or single file only

read locks do not block additional read locks being made, but block something from getting a write lock on a file till all read locks have been purged

write locks block everything including other write locks

if there's any locking in the LockTrie I wrote, the blocked request goes into a request trie

when a file is released from locks in the lock trie, then that file path is returned by the lock trie and I can look for all requests in the requests trie that fit that path

in order of arrival hopefully

Martijn Hoekstra

@martijnhoekstra

So the trie holds requests to lock some file or directory. And when a lock is released, you want to find the oldest request waiting for that file to become available

Mark Hammons

@markehammons

yep

so, startTime is useful for that, but the problem is its granularity is ms

in my tests, I can allocate requests much faster than 1 per ms, unless I use Thread.sleep

Martijn Hoekstra

@martijnhoekstra

if that's the issue, just impose an artificial ordering key on it

Mark Hammons

@markehammons

so, my thoughts on that was using a private AtomicLong in the LockRequest companion object, with a method to get the next long and increment

only problem is of course the point which the Long value overflows

Martijn Hoekstra

@martijnhoekstra

do you need to sweat that? There are a lot of Long values

Mark Hammons

@markehammons

in that case, if there were two requests, started at the same ms, in the same node, and one rolled over to negative then technically it would go first

i'm guessing no personally. i think in the case of that particular blue moon, it's ok if ordering is violated just once

the other request will still get served eventually, it'll just have to wait a little longer than it normally would

Martijn Hoekstra

@martijnhoekstra

I suspect it's likelier that your disk wears out before you did your 2.147.483.647 lock requests on it than the other way round

Mark Hammons

@markehammons

well, this is going on a raid system so in theory i could just keep replacing the disks :p

Martijn Hoekstra

@martijnhoekstra

well, back to the drawing board then :P

Mark Hammons

@markehammons

but also, i'd have more like 9,223,372,036,854,775,808 lock requests before overflow is even possibly an issue if I started the counter at 0, but I'm starting at Long.MinValue, so it's more like 1.844674407370955e19

Martijn Hoekstra

@martijnhoekstra

so I think we can call that good :D

Where communities thrive

People

Repo info

Activity