Common Code Items

Before we dig into each implementation, I want to cover a few things that are common to most of the examples. The first thing they share is the following enum.

# #![allow(unused_variables)]
#fn main() {
enum DurationPart {

This is going to be how we represent each of the parts of a duration as we are parsing the input. Once parsing is done we will combine them into a full representation of a duration.

# #![allow(unused_variables)]
#fn main() {
pub struct Duration {
    years: Option<f32>,
    months: Option<f32>,
    weeks: Option<f32>,
    days: Option<f32>,
    hours: Option<f32>,
    minutes: Option<f32>,
    seconds: Option<f32>,

The next thing that pops up across multiple crates is the need to parse a string into a float.

quick note:, the values are not actual floating point numbers as the spec does not allow for scientific notation (1.2e-3), they would be more akin to the decimal data type provided in some languages.

For this we are going to lean on the implementation in the standard library so it will typically just look like this.

# #![allow(unused_variables)]
#fn main() {
let value_str = "1.222";
let value: f32 = value_str.parse();

Here the parse method on &str returns a result, so we would need to deal with that as well.

The last thing to cover here is that each parser will need to deal with the fact that M can mean either month or minute. While there isn't a shared code solution for this, it does pop up a few times.