Crate cc_traits

This crate provide traits to describe common operations available on data structures. This is particularly useful when building new types on top of generic data structures without relying on the actual implementation of the underlying data structure.

Here is an example of the kind of traits provided by this crate:

/// Mutable collection where new elements can be inserted.
pub trait Insert: Collection {
	/// The output of the insertion function.
	type Output;
 
	/// Insert a new element in the collection.
	fn insert(&mut self, element: Self::Item) -> Self::Output;
}

Usage

Such traits can be used to define collections with special properties, indepently of the actual internal data structure. For instance the following code defines an Ordered<S> stack collection, guarantying the well-sortedness of the elements in the stack.

use cc_traits::{
	Collection,
	Back,
	PushBack
};
 
/// Ordered stack.
pub struct Ordered<S> {
	inner: S
}
 
impl<S> Ordered<S> {
	pub fn new() -> Self where S: Default {
		Ordered {
			inner: S::default()
		}
	}
}
 
impl<S> Ordered<S> {
	/// Push the given element on the stack iff it is grater or equal
	/// to every other element already in the stack.
	pub fn try_push<T>(&mut self, element: T) -> Result<(), T>
	where
		T: PartialOrd,
		S: Collection<Item=T> + Back + PushBack // `S` must be a stack providing `back` and `push_back`.
	{
		if self.inner.back().map(|back| back <= &element).unwrap_or(true) {
			self.inner.push_back(element);
			Ok(())
		} else {
			Err(element)
		}
	}
}
 
fn main() {
	let mut vec: Ordered<Vec<i32>> = Ordered::new(); // a `Vec` is a stack so it works.
 
	assert!(vec.try_push(1).is_ok());
	assert!(vec.try_push(2).is_ok());
	assert!(vec.try_push(0).is_err());
 
	use std::collections::VecDeque;
	let mut deque: Ordered<VecDeque<i32>> = Ordered::new(); // a `VecDeque` is also a stack.
 
	assert!(deque.try_push(1).is_ok());
	assert!(deque.try_push(2).is_ok());
	assert!(deque.try_push(0).is_err());
}

Trait aliases

By enabling the nightly you can get access to some trait alias definitions that can be useful to reduce the verbosity of your code. Here is an example of such aliases defining the common interface of stacks:

pub trait Stack<T> = Collection<Item=T> + Len + Back;
pub trait StackMut<T> = Stack<T> + BackMut + PushBack + PopBack;

Standard library

By default, all the traits defined in this crate are implemented (when relevent) for the standard library collections. You can disable it by using the nostd feature.

Foreign implementations

In addition to the standard library, traits are implemented for some popular crates if you enable the feature of the same name. Here are the supported crates:

• slab providing the Slab collection.
• smallvec providing the SmallVec collection.

Traits

Back	Collection exposing a reference to its back element.
BackMut	Collection exposing a mutable reference to its back element.
Capacity	Collection with known capacity.
Clear	Clearable collection.
Collection	Abstract collection.
Front	Collection exposing a reference to its front element.
FrontMut	Collection exposing a mutable reference to its front element.
Get	Queryable collection.
GetMut	Mutably queryable collection.
Insert	Mutable collection where new elements can be inserted.
Len	Sized collection.
MapInsert	Mutable map where new new key-value pairs can be inserted.
PopBack	Mutable collection where elements can be popped from the back.
PopFront	Mutable collection where elements can be popped from the front.
PushBack	Mutable collection where new elements can be pushed on the back.
PushFront	Mutable collection where new elements can be pushed on the front.
Remove	Mutable collection where elements can be removed from.
Reserve	Collection that can extend their capacity.
WithCapacity	Collection that can be created with a minimum given capacity.