rust/library/core
Lyndon Brown 169c59ff0f Add some core::cmp::Ordering helpers
...to allow easier greater-than-or-equal-to and less-than-or-equal-to
comparisons, and variant checking without needing to import the enum,
similar to `Option::is_none()` / `Option::is_some()`, in situations where
you are dealing with an `Ordering` value. (Simple `PartialOrd` / `Ord`
based evaluation may not be suitable for all situations).

Prior to Rust 1.42 a greater-than-or-equal-to comparison might be written
either as a match block, or a traditional conditional check like this:

```rust
if cmp == Ordering::Equal || cmp == Ordering::Greater {
    // Do something
}
```

Which requires two instances of `cmp`. Don't forget that while `cmp` here
is very short, it could be something much longer in real use cases.

From Rust 1.42 a nicer alternative is possible:

```rust
if matches!(cmp, Ordering::Equal | Ordering::Greater) {
    // Do something
}
```

The commit adds another alternative which may be even better in some cases:

```rust
if cmp.is_ge() {
    // Do something
}
```

The earlier examples could be cleaner than they are if the variants of
`Ordering` are imported such that `Equal`, `Greater` and `Less` can be
referred to directly, but not everyone will want to do that.

The new solution can shorten lines, help avoid logic mistakes, and avoids
having to import `Ordering` / `Ordering::*`.
2020-12-10 20:32:12 +00:00
..
benches Remove redundant 'static from library crates 2020-10-18 17:25:51 +02:00
src Add some core::cmp::Ordering helpers 2020-12-10 20:32:12 +00:00
tests Make ui test that are run-pass and do not test the compiler itself library tests 2020-11-30 02:47:32 +01:00
Cargo.toml mv std libs to library/ 2020-07-27 19:51:13 -05:00