Crate fera_optional
source ·Expand description
An optional value trait and some implementations.
There are two main uses for this:
- To abstract over the representation of optional values in generic code
(
Optional
trait); - To represent optional value in a space efficient way (
OptionalBool
,OptionalMax
,OptionalMin
, etc).
Note that this is complementary to std::option::Option
, not a replacement. The idea is to
use std::option::Option
interface by converting an Optional
value to an
std::option::Option
value.
The optional
crate is similar, but we think that this module is more
generic, mainly because optional
crate is not concerned with the use case 1.
This crate can be used through fera
crate.
Example
One can use OptionalMax<usize>
to represent an optional usize
where the None
value is
represented by usize::MAX
.
use fera_optional::*;
use std::mem;
assert_eq!(mem::size_of::<usize>(), mem::size_of::<OptionalMax<usize>>());
// default
let y = OptionalMax::<usize>::default();
assert_eq!(None, y.into_option());
// from a value
let x = OptionalMax::from(10usize);
assert_eq!(Some(&10), x.to_option_ref());
assert_eq!(10, *x.to_option_ref().unwrap());
// from an optional value
let z = Some(10);
let w = OptionalMax::from(z);
assert_eq!(Some(10), w.into_option());
Using OptionalBool
use fera_optional::*;
use std::mem;
assert_eq!(1, mem::size_of::<OptionalBool>());
let mut x = OptionalBool::from(false);
assert!(!*x.to_option_ref().unwrap());
// change the value
*x.to_option_mut().unwrap() = true;
assert!(*x.to_option_ref().unwrap());
Structs
Creates
T::max_value()
as None
.Creates
T::min_value()
as None
.An
Optional
for bool
with 1 byte size.
std::option::Option<bool>
have size 1 since rustc 1.23.An
Optional
that represents None
with a specified value (B::none()
) of T
domain.Traits
Type Definitions
An
Optional
that uses T::max_value()
as None
.An
Optional
that uses T::min_value()
as None
.