split and join

Split with split and join with join.

split and join

split divides text at a separator and returns an iterator yielding &str pieces. join combines a list of pieces into one text:

let csv = "elma, armut ,kiraz";
let parcalar: Vec<&str> = csv.split(',').map(|p| p.trim()).collect();
println!("{:?}", parcalar);           // ["elma", "armut", "kiraz"]
println!("{}", parcalar.join(" | ")); // elma | armut | kiraz

The pieces are slices of the source; nothing is copied. The source text must live as long as the pieces are used.

Other splitting methods

There are different splitting methods for different situations:

"bir  iki\tüç".split_whitespace()   // ["bir", "iki", "üç"]
"a\nb\nc".lines()                   // ["a", "b", "c"]
"anahtar=değer".split_once('=')     // Some(("anahtar", "değer"))
"a-b-c-d".splitn(2, '-')             // ["a", "b-c-d"]
"a-b-c".rsplit('-')                  // ["c", "b", "a"]

split_whitespace treats several spaces and tabs as one separator; it's the safest for user input.

Exercise CSV line

Split the text let csv = "elma, armut ,kiraz"; into pieces with split(',') and trim, and collect them into a Vec<&str>. Print the vector with {:?} and the result of join(" | "), separated by a space.

Show example solution

fn main() {
    let csv = "elma, armut ,kiraz";
    let parcalar: Vec<&str> = csv.split(',').map(|p| p.trim()).collect();
    println!("{:?} {}", parcalar, parcalar.join(" | "));
}

Test yourself

What is <code>"a,,b".split(',').count()</code>?
- 3 ("a", "", "b")
- 2
- 4
- 1
Show answer

3 ("a", "", "b") — An empty piece appears between two consecutive separators. Use filter(|p| !p.is_empty()) to drop empty ones.

Join the pieces

let p = vec!["a", "b", "c"];
let s = p.____("-");   // "a-b-c"

Show answer

let p = vec!["a", "b", "c"];
let s = p.join("-");   // "a-b-c"

Method and result

"a b c".split_whitespace().count()

3
"a,b".split(',').count()

2
"x=1".split_once('=')

Some(("x", "1"))
["a", "b"].join("+")

"a+b"

Next lesson: Summary - Advanced strings

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