Code shared from the Rust Playground

playground.rs

use std::env;
use std::fs::File;
use std::io::prelude::BufRead;
use std::io::BufReader;
use std::collections::HashMap;

#[derive(Debug)]
struct WordCounter(HashMap<String, u64>);

impl WordCounter {
  fn new() -> WordCounter {
    WordCounter(HashMap::new())
  }

  fn increment(&mut self, word: &str) {
    let key = word.to_string();
    let count = self.0.entry(key).or_insert(0);
    *count += 1;
  }

  fn display(self) {
    for (key, value) in self.0.iter() {
      println!("{}: {}", key, value);
    }
  }
}

fn main() {
  let arguments: Vec<String> = env::args().collect();
  let filename = &arguments[1];
  println!("Processing file: {}", filename);
  let file = File::open(filename).expect("Could not open file.");
  let reader = BufReader::new(file);
  let mut word_counter = WordCounter::new();

  for line in reader.lines() {
    let line = line.expect("Could not read line.");
    let words = line.split(" ");
    for word in words {
      if word == "" {
        continue
      } else {
        word_counter.increment(word);
      }
    }
  }
  word_counter.display();
}