How can I check if a &str consists of only a given slice of chars?

Question

use itertools::Itertools;

fn shifter(s: &str) -> usize {
    s.split(' ')
     .unique()
     .map(|x| x.chars().
}

Im trying to finish up the task to calculate how many "shifter words" a given &str contains without any duplicates. "shifter word" is one that consist only of "H", "I", "N", "O", "S", "X", "Z", "M" and "W".

shifter("SOS IN THE HOME") == 2 // shifter words are "SOS" and "IN"
shifter("WHO IS SHIFTER AND WHO IS NO") == 3 // shifter words are "WHO", "IS", "NO"
shifter("TASK") == 0 // no shifter words
shifter("") == 0 // no shifter words in empty string

Answer 1

You can test if every element matches a given predicate by using Iterator::all() and str::contains.

"SOS".chars().all(|c| "HINOSXZMW".contains(c)); // true

Note that there's also slice::contains, so the following would work as well:

let letters = ['H', 'I', 'N', 'O', 'S', 'X', 'Z', 'M', 'W'];

"SOS".chars().all(|c| letters.contains(&c)); // true

Answer 2

Putting it all together from:

• How to check if a string contains a substring in Rust?
• How to check if string only contains set of characters in Rust?

fn shifter(s: &str) -> usize {
    s.split(' ')
        .unique()
        .filter(|x| !x.is_empty() && x.chars().all(|c| "HINOSXZMW".contains(c)))
        .count()
}

The is_empty() is there because all() returns true for an empty collection.

See it working on the playground.