Clash Royale CLAN TAG#URR8PPP

How to join arrays like JavaScript's destructuring?

I want to make a function that receives a Vec and a position to change a number.

Vec

In JavaScript, this is really simple:

function replaceNumber(line, position, number)
return [
...line.slice(0, position),
number,
...line.slice(position+1, line.length)
]



How can I make a similar function in Rust?

I tried this:

fn replace_number(line: Vec<i32>, point: i32, number: i32) -> Vec<i32>
return [
&line[0..point as usize],
&[number],
&line[point as usize+1, point.len()]
].concat();



The result is an array of arrays. How can I make a destructuring like the JavaScript example?

1 Answer
1

I want to make a function that receives a Vec and a position to change a number.

Rust has indexing syntax, just like JavaScript, so there's really no need for the destructuring.

fn replace_number(mut line: Vec<i32>, point: usize, number: i32) -> Vec<i32>
line[point] = number;
line



or, more idiomatically:

fn replace_number(line: &mut Vec<i32>, point: usize, number: i32)
line[point] = number



Even more idiomatically would be to not have this function, probably, and just write it inline...

I want to know about immutably adding

With your original code, there's zero concern about anything "bad" happening because of mutability:

fn replace_number(line: Vec<i32>, point: i32, number: i32) -> Vec<i32>


This function takes ownership of the Vec, so the concept of immutability is rather moot here — the caller no longer has the Vec to care if it's mutated or not!

Vec

Vec

If you wanted to share data, you'd use a reference (a slice, specifically) like &[i32]. This is inherently immutable — you can't change it if you wanted to. You'd have to clone all the children and make the vector mutable:

&[i32]

fn replace_number(line: &[i32], point: usize, number: i32) -> Vec<i32>
let mut line = line.to_owned();
line[point] = number;
line



If you really wanted something like the JS syntax, you can use concat:

concat

fn replace_number(line: &[i32], point: usize, number: i32) -> Vec<i32>
[&line[..point], &[number], &line[point + 1..]].concat()



See also:

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