word_count.rb

my_string.scan(/[a-z\d]+/).each_with_object(Hash.new(0)){ |e, a| a[e] += 1 }

word_count.rs

use std::collections::HashMap;

fn split_text(c: char) -> bool {
    !c.is_alphanumeric()
}

fn fold_words(mut acc: HashMap<String, u32>, word: &str) -> HashMap<String, u32> {
    if word.len() > 0 {
        let count = acc.entry(word.to_lowercase()).or_insert(0);
        *count += 1;
    }
    acc
}

pub fn word_count(text: &str) -> HashMap<String, u32> {
    text.split(split_text).fold(HashMap::new(), fold_words)
}