Calculate the length of the common prefix of two slices

df_prefix_len.rs

/*
  Calculats the length of the common pfix of two slices.
  The slices a and b are zipped, leading to an iterator containing a tuple with a component of each of the input iterators
  The iterators take care of handling different-sized slices (also slices of zero size)
*/
fn common_prefix_len(a: &str, b: &str) -> usize {
  a.chars().zip(
      b.chars()
  ).take_while(
    |(x, y)| x == y
  ).count()
}