binary-heap-plus 0.1.3

# binary-heap-plus-rs

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Enhancement over Rust's `std::collections::BinaryHeap`.

It supports the following features and still maintains backward compatibility.
- Max heap
- Min heap
- Heap ordered by closure
- Heap ordered by key generated by closure

You can change the line

```
use std::collections::BinaryHeap;
```

to like below.

```
use binary_heap_plus::*;
```

Your code will compile as before unless you use unstable APIs.

This crate requires Rust 1.26 or later.

# Added muthods

## `BinaryHeap::new_xxx()`

- (original) `::new()`     // creates a max heap
- `::new_min()` // creates a min heap
- `::new_by(f)` // creates a heap ordered by the given closure `f`
- `::new_by_key(g)` // creates a heap ordered by key generated by the given closure `g`

## `BinaryHeap::with_capacity_xxx()`

- (original) `::with_capacity(n)` // creates a max heap with capacity `n`
- `::with_capacity_min(n)` // creates a min heap with capacity `n`
- `::with_capacity_by(n, f)` // creates a heap with capacity `n`, ordered by the given closure `f`
- `::with_capacity_by_key(n, g)` // creates a heap with capacity `n`,  ordered by key generated by the given closure `g`

## Future

In future, the trait `Compare<T>` might be replaced with `FnMut(&T, &T) -> Ordering`.

To do that, rustc needs to stabilize a few unstable features.

## References

See the following discussions for the background:
- https://internals.rust-lang.org/t/pre-rfc-binaryheap-flexibility/7482
- https://users.rust-lang.org/t/binaryheap-flexibility-revisited-supporting-other-than-max-heap/17062
- https://users.rust-lang.org/t/binaryheap-flexibility/8766
- https://github.com/rust-lang/rust/issues/38886