One of the things that I'd like to see for the Rust Book is some form of "Here's how to use it in a function".

For example, Taking a random piece of code from the Rust Book

    let buffer: &mut [i32];
    let coefficients: [i64; 12];
    let qlp_shift: i16;

    for i in 12..buffer.len() {
        let prediction = coefficients.iter()
                                     .zip(&buffer[i - 12..i])
                                     .map(|(&c, &s)| c * s as i64)
                                     .sum::<i64>() >> qlp_shift;
        let delta = buffer[i];
        buffer[i] = prediction as i32 + delta;
    }

How would one break part of this into a function

    fn get_part ??? What might go here ???  

    let buffer: &mut [i32];
    let coefficients: [i64; 12];
    let qlp_shift: i16;

    for i in 12..buffer.len() {
        let prediction = get_part(&coefficients,&buffer,i)
                                     .map(|(&c, &s)| c * s as i64)
                                     .sum::<i64>() >> qlp_shift;
        let delta = buffer[i];
        buffer[i] = prediction as i32 + delta;
    }

[Exercise for the reader] I'm not sure If I could write the code to do this without taking a few wrong turns.