Chunking a vector of strings - rust

Question

I'm trying to chunk an vector of uneven length strings into a vector of even length strings. The laziest way I could think of doing this is to join the arguments into a string, convert the chars to a vector, and then use Vec::chunks. Unfortunately, I'm running into issues trying to collect the chunks into strings.
let args: Vec<String> = ["123", "4", "56"].iter().map(|&s| s.into()).collect();
let result: Vec<String> = args
.join(" ")
.chars()
.collect::<Vec<_>>()
.chunks(2)
.map(|c| c.collect::<String>())
.collect::<Vec<String>>();
assert_eq!(["12", "34", "56"], result);
Results in the error:
error[E0599]: no method named `collect` found for type `&[char]` in the current scope
--> src/main.rs:9:20
|
9 | .map(|c| c.collect::<String>())
| ^^^^^^^
|
= note: the method `collect` exists but the following trait bounds were not satisfied:
`&mut &[char] : std::iter::Iterator`
`&mut [char] : std::iter::Iterator`

Answer 1

You weren't far off:
let result: Vec<String> = args
.join("")
.chars()
.collect::<Vec<_>>()
.chunks(2)
.map(|x| x.iter().cloned().collect())
.collect();
println!("{:?}", result);
You probably don't want a space when joining them together.
You need to convert each chunk (which is a &[char]) into an iterator via .iter(). You then have to convert the iterated type from a &char to a char via .cloned().
I might write this using Itertools::chunks though:
use itertools::Itertools; // 0.8.0
fn main() {
let args = ["123", "4", "56"];
let together = args.iter().flat_map(|x| x.chars());
let result: Vec<String> = together
.chunks(2)
.into_iter()
.map(|x| x.collect())
.collect();
println!("{:?}", result);
}
flat_map avoids the need to create a String, it just chains one iterator to the next.
Itertools::chunks allows the programmer to not create an intermediate Vec. Instead, it has an internal vector that, IIRC, will only store up to n values in it before yielding a value. This way you are buffering a smaller amount of items.