2 releases
0.1.1 | Feb 9, 2020 |
---|---|
0.1.0 | Feb 8, 2020 |
#136 in #issue
3KB
is-same
This crate provides the IsSame trait, which is specifically for diffing immutable data that has been transformed. The trait differs from PartialEq in some important ways:
- Floating point values are compared by their bit patterns, preventing
NaN values from making a data structure permanently compare as not
equal to itself. This also lets you detect a value changing from
-0.0
to0.0
. - Referential equality is used to make comparisons more efficient. The
library assumes that the contents of
Rc<T>
andArc<T>
are immutable and can't change, so they only need to be compared by their pointers.
This trait is implemented out of the box for a lot of standard library types, but if any are missing feel free to file an issue or contribute a PR. Issues relating to error messages or other usability issues (including with the proc macro) are also welcome!
The trait is explicitly not implemented for interior mutability types (Cell, RefCell, AtomicUSize, Mutex, etc.), as this would make the assumptions based on referential equality unsound. This could be changed in the future if it presents a problem.
Install
Add to your Cargo.toml
:
is-same = "0.1"
is-same-derive = "0.1"
Usage
use is_same::IsSame;
use is_same_derive::IsSame;
#[derive(IsSame)]
struct MyStruct {
text: String,
foo: usize,
bar: char,
}
fn diff(left: &MyStruct, right: &MyStruct) {
println!("is_same? {}", left.is_same(right));
}
Dependencies
~1.5MB
~36K SLoC