On 12/7/12 11:58 AM, Steve Jenson wrote:
Hi rust gurus,
Today I ported the purely functional Pairing Heap found in Okasaki's
Purely Functional Data Structures to Rust. I was hoping that some of you
might take a look at it and give me feedback on where I could be using
Rust's idioms better.
https://github.com/stevej/rustled/blob/master/pairing_heap.rs
The code I wrote is a little longer than Okasaki's example, mostly due
to Standard ML's more concise pattern matching. (see page 54 for
comparison) Is there a way to do pattern matching in argument lists as
in Haskell or SML?
Yes, in Rust 0.5 this works.
I noticed several things:
* Using explicit self (&self) will help make your levels of indirection
consistent between `self` and `other` in a few functions. This works
better in 0.5 than it does in 0.4.
* Braces aren't necessary after the => in patterns unless you want
multiple statements.
* I'm confused as to why you need an @record as your type in
PairingHeap_ (note that records are deprecated in favor of structs). In
Rust 0.5 you can say
pub enum PairingHeap<E:Copy Eq Ord> {
Empty,
PairingHeapCell {
head: E,
rest: @List<PairingHeap<E>>
}
}
* You can use "self" as the return value in a trait.
* In 0.5 you can use #[deriving_eq] for your enum to avoid writing the
Eq definition, although I'm not sure that works for struct-like enum
variants as in PairingHeapCell above (I should check this).
* @ signs are required for pattern matching because pattern matching
never dereferences through pointers implicitly.
* You have a bunch of "return" expressions in which "return" can be left
off.
* Some of your if statements could be replaced with pattern guards.
* is_empty() could just be:
pure fn is_empty(&self) -> bool { *self == Empty_ }
Patrick
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