mikecargal

mikecargal

Hands-on Rust: clone_dirty cloning HashSet

Title: Hands-On Rust (Chapter 10)

This has been bugging me a bit since coding it, so I tried the change and it seems to work.

Isn’t it a bit expensive to clone a HashSet that you intend to immediately replace?

I tried the following change to clone_dirty(&self) -> Self

    pub fn clone_dirty(&self) -> Self {
        // let mut cloned = self.clone(); // TODO: isn't this expensive??
        // cloned.is_dirty = true;
        // cloned
        Self {
            visible_tiles: HashSet::new(),
            radius: self.radius,
            is_dirty: true,
        }
    }

Game play seems to be working fine so far. I’m assuming that creating a new HashSet is less expensive than closing a populated HashSet. That also raised the question for me as to whether visible_tiles should be Option instead and the None would serve the same purpose as is_dirty. Maybe I’ll see that this is a bad idea as I progress…

Marked As Solved

herbert

herbert

Author of Hands-on Rust

That’s a good point; clone can be expensive (it’s remarkable how well LLVM optimizes it out, especially on release builds). There’s a bit of compiler magic that notices that it’s basically a set of memcpy calls under the hood, and elides them. I like your approach better, though - it’s dangerous to rely on the compiler noticing an optimization when you can tell it what you want.

Adding an is_visible method is also a great idea. I’ll see if I can refactor the book code a little.

I’ll try and merge this into the next beta. Thank you!

Where Next?

Popular Pragmatic Bookshelf topics Top

jimmykiang
This test is broken right out of the box… — FAIL: TestAgent (7.82s) agent_test.go:77: Error Trace: agent_test.go:77 agent_test.go:...
New
Mmm
Hi, build fails on: bracket-lib = “~0.8.1” when running on Mac Mini M1 Rust version 1.5.0: Compiling winit v0.22.2 error[E0308]: mi...
New
alanq
This isn’t directly about the book contents so maybe not the right forum…but in some of the code apps (e.g. turbo/06) it sends a TURBO_ST...
New
jskubick
I think I might have found a problem involving SwitchCompat, thumbTint, and trackTint. As entered, the SwitchCompat changes color to hol...
New
nicoatridge
Hi, I have just acquired Michael Fazio’s “Kotlin and Android Development” to learn about game programming for Android. I have a game in p...
New
AufHe
I’m a newbie to Rails 7 and have hit an issue with the bin/Dev script mentioned on pages 112-113. Iteration A1 - Seeing the list of prod...
New
taguniversalmachine
It seems the second code snippet is missing the code to set the current_user: current_user: Accounts.get_user_by_session_token(session["...
New
dachristenson
@mfazio23 Android Studio will not accept anything I do when trying to use the Transformations class, as described on pp. 140-141. Googl...
New
roadbike
From page 13: On Python 3.7, you can install the libraries with pip by running these commands inside a Python venv using Visual Studio ...
New
dachristenson
I’ve got to the end of Ch. 11, and the app runs, with all tabs displaying what they should – at first. After switching around between St...
New

Other popular topics Top

PragmaticBookshelf
Learn from the award-winning programming series that inspired the Elixir language, and go on a step-by-step journey through the most impo...
New
ohm
Which, if any, games do you play? On what platform? I just bought (and completed) Minecraft Dungeons for my Nintendo Switch. Other than ...
New
AstonJ
Saw this on TikTok of all places! :lol: Anyone heard of them before? Lite:
New
AstonJ
If you get Can't find emacs in your PATH when trying to install Doom Emacs on your Mac you… just… need to install Emacs first! :lol: bre...
New
New
AstonJ
Was just curious to see if any were around, found this one: I got 51/100: Not sure if it was meant to buy I am sure at times the b...
New
hilfordjames
There appears to have been an update that has changed the terminology for what has previously been known as the Taskbar Overflow - this h...
New
PragmaticBookshelf
Build modern server-driven web applications using htmx. Whatever programming language you use, you’ll write less (and cleaner) code. ...
New
AstonJ
If you’re getting errors like this: psql: error: connection to server on socket “/tmp/.s.PGSQL.5432” failed: No such file or directory ...
New
PragmaticBookshelf
A concise guide to MySQL 9 database administration, covering fundamental concepts, techniques, and best practices. Neil Smyth MySQL...
New

Sub Categories: