Separation of features into separate crates

[PTaylor-us]

It may be necessary to split this crate as there are potentially different use-cases for various features.

[PTaylor-us]

My initial impression is that the following discrete crates might make sense:

• time
  • Duration trait and off-the-shelf duration types
  • Rate types
• clock
  • Clock trait
  • Instant type
  • Dependencies
    • time
• timer
  • Timer type
  • Dependencies
    • clock

Largely, these dependencies are already realized. However the Clock trait contains a method new_timer() to spawn --- you guessed it, a new Timer. I like the composition given this structure:

let timer = clock.new_timer(2.seconds()).start();

If the timer functionality is separated from the Clock trait, we're left with:

let timer = Timer::new(my_clock, 2.seconds()).start();

Definitely not nearly as pretty. Any suggestions?

[hannobraun]

If the timer functionality is separated from the Clock trait, we're left with:

let timer = Timer::new(my_clock, 2.seconds()).start();

Definitely not nearly as pretty. Any suggestions?

Add an extension trait to timer (pseudo-code, not compiled or tested):

pub trait ClockExt { // alternative name: `NewTimer`
    fn new_timer(duration) -> Timer { ... }
}

impl<T> ClockExt for T where T: Clock {}

That would require the user to import ClockExt to use that method, but that can be eased by creating a prelude module and telling users to always use timer::prelude::*.