Advertisements I’m writing a simple game engine in C++. I’m very late to C++, because I’ve spent most of my free time with C, so the unique_ptr, shared_ptr and all of this ownership magic is hardly understandable for me. I stumbled upon one thing that I can’t understand at all. Let’s have a following snippet:… Read More How does the std::unique_ptr&& function argument work?
Advertisements I’m new to Rust and write a library for linear algebra on binary matrices. I have a sparse matrix struct storing a matrix in column major format (CscMatrix). The CscMatrix stores the positions of ones in each column, each column takes up a contiguous segment in the ‘ones’ vector. The index of the first… Read More Can I create an immutable vector from another immutable vector in Rust without copying?
Advertisements I’m trying to learn Rust and am using the advent of code to do so. I’ve just started and have decided to have a vector containing "Elf" structs, of which each will contain a vector calory_items. I’m trying to create this from a text file and have the following code: use std::io::{self, BufReader}; use… Read More How can I create a vector of structs in a loop
Advertisements I would like to write a type that has an implementation for the Drop trait. but I would like to not need to call .clone() every time I need a copy like a type that implement Copy. But from what I understood, I cannot use the Copy trait because it can only be implemented… Read More How to implement value-like semantics for non-trivial types in rust
Advertisements My question aims at understanding a deeper variant of the "cannot move out of index" error, specifically when I want to move a field of a struct that resides in a vector. Below is a classical example of a vector of objects and an attempt to move a field out of it. struct Foo… Read More Moving a field of an object in vector index
Advertisements I have a struct struct Triangle { normal: Normal, vertices: [Vertex; 3], } that I’d like to deserialize from a Read type. I thought implementing TryFrom would be idiomatic since I’m turning a stream of bytes into a Triangle but it may fail. impl TryFrom<&mut dyn std::io::Read> for Triangle { type Error = std::io::Error;… Read More Is there a way to prevent try_from from consuming a mutable reference?
Advertisements I’m trying to implement a simple hash table with external chaining in Rust but having trouble with the table declaration. I declared the table as such: static mut _HASH_TABLE: [Option<Box<MemoryMap>>; (std::u16::MAX -1) as usize] = [None; (std::u16::MAX -1) as usize]; with the MemoryMap being a dynamic linked list pub struct MemoryMap { entry: SimpleEntry,… Read More Implement `Copy` trait for `Option<Box<Struct>>`
Advertisements I can’t understand why I am getting this error below: ` error[E0502]: cannot borrow `*s` as mutable because it is also borrowed as immutable –> src/main.rs:8:5 | 7 | let char_h = s.get(0..0).unwrap().clone(); | ———– immutable borrow occurs here 8 | s.replace_range(0..0, "h"); | ^^^^^^^^^^^^^^^^^^^^^^^^^^ mutable borrow occurs here 9 | println!("char before {char_h}… Read More Why borrow persists after clone
Advertisements enum List<‘a> { Cons(isize, &’a List<‘a>), Nil, } fn main() { use List::*; use slotmap::SlotMap; let mut table = SlotMap::new(); let nil = table.insert(Nil); table.insert(Cons(1, table[nil])); } SlotMap<K: Key, V>‘s insert is pub fn insert(&mut self, value: V) -> K and its impl<K: Key, V> Index<K> is fn index(&self, key: K) -> &V So… Read More How to get many references to one object, using SlotMap?
Advertisements I’d like to keep an instance of the handlebars registry in a struct named "Mailer". The instance is to be initialized upon running the "new" function of the Mailer implementation. I do have massive problems in figuring out the proper ownership at each scope. use handlebars::Handlebars; pub struct Mailer<‘reg> { registry: &’reg handlebars::Handlebars<‘reg> }… Read More Assign a struct implementation to another struct implementation