Questions tagged [vec]
78 questions
17
votes
3 answers
Error[E0277]: the type `[u32]` cannot be indexed by `u32`
What am I doing wrong with the variable i below? Why does the compiler say I cannot index a Vec with a u32 and how do I fix it?
fn main() {
let a: Vec = vec![1, 2, 3, 4];
let number: u32 = 4;
let mut count = 0;
for i in…
Masaki Imai
- 181
- 1
- 1
- 3
9
votes
4 answers
Checking a Vec to see if it's all zero?
I have many 4KiB buffers, which have a 50% chance of containing only zero values. The non-zero buffers will typically have a non-zero byte early in the buffer.
fn is_zero(buf: &Vec) -> bool {
for byte in buf.into_iter() {
if *byte…
fadedbee
- 42,671
- 44
- 178
- 308
7
votes
2 answers
How to have a vec of Boxes which implement 2 traits?
In rust I would like to have a vec containing items which implement 2 traits. However when I try to implement it like so, I get the error only auto traits can be used as additional traits in a trait object:
let mut v : Vec
geeks_kick
- 151
- 7
7
votes
2 answers
How to write file from Vec?
I have a base64 image and got Vec from it and write them to a file.
Here is my code:
let file_contents_base64: Vec = image_base64::from_base64(
String::from(&file_contents_string_vec[0])
);
I want to write the file_contents_base64…
Pixel Coder
- 139
- 1
- 1
- 6
6
votes
1 answer
How to Convert vector into json in rust
everyone, I just came into contact with rust recently, and now I want to use rust to write a static website. Now I have a very basic problem. The code is as follows:
pub struct Post {
title: String,
created: String,
link: String,
…
lanqy
- 3,001
- 5
- 25
- 18
5
votes
1 answer
Can I hold a pointer (unsafely) to an element of Vec while the Vec is being moved?
I'm implementing an algorithm, and in order to maintain the desired time complexity, I would like to hold a pointer to an element of a Vec while the Vec is being moved.
Specifically, something like this:
fn main() {
let mut v: Vec =…
Bernard
- 5,209
- 1
- 34
- 64
5
votes
3 answers
How can I retain vector elements with their original index?
If I have a Vec I can iterate over elements using an index via v.iter().enumerate(), and I can remove elements via v.retain(). Is there a way to do both at once?
In this case the index could no longer be used to access the element - it would be the…
Timmmm
- 88,195
- 71
- 364
- 509
4
votes
0 answers
Why can I initialize but not assign a &vec![]?
What is the difference between assign after binding to var and direct assign a &Vec.
let mut v2 = &vec![1,2,3];
let tv = &vec![2,3,4];
v2 = tv;
// different from
// v2 = &vec![2, 3, 4]; // uncomment this will error
println!("{:?}", v2);
borrow…
BruceChar
- 83
- 1
- 5
4
votes
3 answers
Is Vec::splice() efficient when the length doesn't change?
When you use Vec::splice() to replace part of a Vec, is it smart enough to specially handle the case where the replacement is the same length as the chunk it is replacing, or should I handle that myself?
Is there any point doing this, or is…
Timmmm
- 88,195
- 71
- 364
- 509
4
votes
4 answers
Rustlings Exercise Traits2, Implement Trait on Vec
The exercise requires me to Implement the trait to Vec. The tests are there and they are failing, which is a good place to start. I've done the trait implementation for the String and it was easy, Vec is another story. I'm not sure what the method…
woss
- 933
- 1
- 11
- 20
3
votes
1 answer
Why can't you convert containers using .into() if the elements can be converted?
If I have a Vec I can't convert it into Vec directly using .into() even if I can convert T into U using .into(). For example this code does not compile:
use std::convert::From;
struct A {
x: i32,
}
struct B {
y: u64,
}
impl From…
Timmmm
- 88,195
- 71
- 364
- 509
3
votes
2 answers
Builtin for checking if vec contains specified element
Let's say, I have a vec containing a list of integers that may be non-continuous (due to element being removed from database).
Example:
$occupiedNumbers = vec[1, 2, 3, 5, 6, 8, 10, 11, 12, 13, 15, 16];
Now what I need is to check if this vec…
Lukasz032
- 354
- 4
- 14
3
votes
1 answer
Vector pop() returns Option
I am beginner in rust. I see pop() method of vector returns
Fel AA
- 303
- 5
- 16
2
votes
2 answers
Is it better to return an Option of a Vec, or just a Vec?
Suppose I am writing a function that takes a bunch of string and filters out the "bad" ones.
The function then returns some strings, but there is a chance that all the strings are filtered out.
So I am wondering, should I use to Option here? I could…
Jim
- 3,821
- 1
- 28
- 60
2
votes
1 answer
Difficulty in trying to implement a type-safe `at` for length-indexed vectors
I have just learnt about the DataKinds extension, type-level literals, and found out that type-levels natural numbers can be compared using constraints provided in the Data.Type.Ord such as (>), and manipulated using type-level operations provided…
Futarimiti
- 551
- 2
- 18