Make functions const where possible

[iliekturtles]

Requires Rust 1.31 for support. Bump requirement for v1.0 or continuing to wait on feature until v2.0? What methods can be const besides new. Will const fn make zero constants easier (#26)?

[Maher4Ever]

Is there an update on this issue? It would great to allow defining quantities in a const variable as shown in #26:

const UNIX_EPOCH_DELTA: Time = Time::new::<time::second>(11644473600.0);

[iliekturtles]

No updates yet. I just haven't had/made the time to get to it. PRs very welcome if anyone wants to tackle this. I would probably start by dropping a const in front of everything and then seeing what sticks.

[adamreichold]

I would probably start by dropping a const in front of everything and then seeing what sticks.

I am not sure this is currently possible for all storage types, e.g. for floating-point numbers the conversion to the system's base unit generally involves floating-point arithmetic which is still unstable behind the feature const_fn_floating_point_arithmetic. This would again leave us with #26 (comment) to create constant quantities.