Well, the functional crowd won. An example expression from the parent article:

    let idx = args
    // iterate over our arguments
    .iter()
    // open each file
    .map(|fname| (fname.as_str(), fs::File::open(fname.as_str())))
    // check for errors
    .map(|(fname, f)| {
      f.and_then(|f| Ok((fname, f)))
        .expect(&format!("input file {} could not be opened", fname))
    })
    // make a buffered reader
    .map(|(fname, f)| (fname, io::BufReader::new(f)))
    // for each file
    .flat_map(|(f, file)| {
      file
        // read the lines
        .lines()
        // split into words
        .flat_map(|line| {
          line.unwrap().split_whitespace()
            .map(|w| w.to_string()).collect::<Vec<_>>().into_iter()
        })
      // prune duplicates
      .collect::<HashSet<_>>()
        .into_iter()
        // and emit inverted index entry
        .map(move |word| (word, f))
    })
  .fold(HashMap::new(), |mut idx, (word, f)| {
    // absorb all entries into a vector of file names per word
    idx.entry(word)
      .or_insert(Vec::new())
      .push(f);

Is there editor support for indenting this stuff?