ciel

ciel

Hands-on Rust: potential bugs

I’ve caught up with B4.0. Quite enjoying it! I ran into a couple of “bugs” in the dungeon crawler game logic. I’ll point out what I am seeing, but maybe you can leave the implementation to the reader to try and figure out as a challenge.

  1. Chasing/Random movement: movers do not consider other intent_to_move when moving to the same destination at the same time. This causes mobs to converge onto the same tile. like this:

  2. The map building flow does not verify that amulet/exit positions are excluded from potential monster/item spawn positions (or vice-versa). While this isn’t an issue for the mobs (since they move), this can cause an item to be placed on top of the exit/amulet. There’s a few easy ways to fix this, but a solution in the book might require a more strict/safe solution to prevent confusion. In the current code the ordering of amulet/monster spawn lines in the implemented build() functions don’t particularly matter, but a fix for this could require a specific order.

I think the book itself prepared me to solve both of these problems on my own. Perhaps it could be something to point out to the users so they have a challenge for themselves to try and solve.

Also, It’s possible content in the future chapters might make these bugs not really relevant.

Most Liked

herbert

herbert

Author of Hands-on Rust

Thanks! This is actually a tough one to find a balance (see mikecargal’s threads on procgen for another example). On one level, I’ve had to restrain myself a bit to keep focused on teaching Rust and concepts rather than bogging down into fine details; on the other hand, it would be really nice to catch these bugs (if I had a third hand, it would be remining me that I have a page count limit!). I intend to tackle some of this (particularly constraining item placement), but probably not all of it.

My current plan is to add some constraints to item placement, at the level of generating available spawn positions. It’s relatively easy to add a few “denied” slots (such as the exit) - so it won’t be too large or trash the reader’s flow too much by vanishing down an aside. I’m hoping to squeeze in a few procgen constraints, too - a quick call to add a forced boundary around the map, maybe cull unreachable tiles (that’s easy to do). Exactly how much of that I can get in is itself constrained by page count. Worst case, it’ll be presented as a “here’s some ideas to improve this” exercise.

The monster overlap is worth discussing a little because it highlights one of the toughest issues with an ECS design. When you are building your systems to run efficiently with little data-overlap from other systems, and each entity effectively processing independently - it does make checking against other dynamic entities harder than you’d expect.

In the Rust Roguelike Tutorial (my big project before this one), I had a whole “blocked” system with an additional data construct to track tile contents. With hindsight, that was a mistake - deep into “second system syndrome”, I spent as much time catching cache invalidation problems (it’s basically a location cache) as I did benefiting from it. So I knew that this book shouldn’t go that route. It does have the nice side-effect that mobs will realize a dynamic path is unavailable and route around to attack from a different direction - but it gets huge and complex achieving that.

So I’m going to do some debugging and get the “collisions lite” setup I was aiming for working better. Check “wants to move” message destinations and simply not apply them if they result in a goblin cheerleading pyramid. I’ve been planning to clean-up the did_something code for that system anyway; it is messier than it needs to be.

Thanks, and I hope my overly long reply makes sense!

ciel

ciel

Absolutely makes sense. The dungeon crawler being built from the book is serving a specific purpose. And a bug free game isn’t the primary goal. Of course, it’d be nice, but not the primary goal. I mostly just wanted to point out cases I saw. What code should not go into the book is just as important to consider when you’re trying to teach a point.

Second system syndrome is quite the siren’s song. Making a buggy game has more value than spending all your time building an overly complex system for a game that you might not finish. I tend to still try to make the overly complex system. :sweat_smile:

Where Next?

Popular Pragmatic Bookshelf topics Top

simonpeter
When I try the command to create a pair of migration files I get an error. user=> (create-migration "guestbook") Execution error (Ill...
New
fynn
This is as much a suggestion as a question, as a note for others. Locally the SGP30 wasn’t available, so I ordered a SGP40. On page 53, ...
New
digitalbias
Title: Build a Weather Station with Elixir and Nerves: Problem connecting to Postgres with Grafana on (page 64) If you follow the defau...
New
Charles
In general, the book isn’t yet updated for Phoenix version 1.6. On page 18 of the book, the authors indicate that an auto generated of ro...
New
New
adamwoolhether
Is there any place where we can discuss the solutions to some of the exercises? I can figure most of them out, but am having trouble with...
New
EdBorn
Title: Agile Web Development with Rails 7: (page 70) I am running windows 11 pro with rails 7.0.3 and ruby 3.1.2p20 (2022-04-12 revision...
New
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

AstonJ
You might be thinking we should just ask who’s not using VSCode :joy: however there are some new additions in the space that might give V...
New
AstonJ
I ended up cancelling my Moonlander order as I think it’s just going to be a bit too bulky for me. I think the Planck and the Preonic (o...
New
dimitarvp
Small essay with thoughts on macOS vs. Linux: I know @Exadra37 is just waiting around the corner to scream at me “I TOLD YOU SO!!!” but I...
New
Exadra37
I am asking for any distro that only has the bare-bones to be able to get a shell in the server and then just install the packages as we ...
New
PragmaticBookshelf
Learn different ways of writing concurrent code in Elixir and increase your application's performance, without sacrificing scalability or...
New
DevotionGeo
The V Programming Language Simple language for building maintainable programs V is already mentioned couple of times in the forum, but I...
New
mafinar
Crystal recently reached version 1. I had been following it for awhile but never got to really learn it. Most languages I picked up out o...
New
New
First poster: joeb
The File System Access API with Origin Private File System. WebKit supports new API that makes it possible for web apps to create, open,...
New
mindriot
Ok, well here are some thoughts and opinions on some of the ergonomic keyboards I have, I guess like mini review of each that I use enoug...
New

Sub Categories: