Crate cc_traits

Expand description

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, independently 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`.
        for<'a> S::ItemRef<'a>: PartialOrd<&'a T> // The reference type must be comparable with other reference types.
    {
        if self.inner.back().map(|back| back <= &element).unwrap_or(true) {
            self.inner.push_back(element);
            Ok(())
        } else {
            Err(element)
        }
    }
}

#[cfg(feature = "std")]
fn ordered_stack_usage<S>()
where
    S: Default + Collection<Item = i32> + Back + PushBack,
    for<'a> S::ItemRef<'a>: PartialOrd<&'a i32>,
{
    let mut ordered: Ordered<S> = Ordered::new();
    assert!(ordered.try_push(1).is_ok());
    assert!(ordered.try_push(2).is_ok());
    assert!(ordered.try_push(0).is_err());
}

#[cfg(feature = "std")]
ordered_stack_usage::<Vec<i32>>(); // a `Vec` is a stack so it works.

#[cfg(feature = "std")]
use std::collections::VecDeque;
#[cfg(feature = "std")]
ordered_stack_usage::<VecDeque<i32>>(); // a `VecDeque` is also a stack.

§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;

As of version 0.8.0, those traits are also available without the nightly feature as regular trait definitions.

§Standard library

By default, all the traits defined in this crate are implemented (when relevant) 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.
serde_json providing the Map<String, Value> collection for JSON objects.
ijson providing the IObject and IArray collections.

Macros§

covariant_item_mut: Automatically defines the CollectionMut::upcast_item_mut function using the covariance of the ItemMut<'a> type with regards to 'a.
covariant_item_ref: Automatically defines the CollectionRef::upcast_item_ref function using the covariance of the ItemRef<'a> type with regards to 'a.
covariant_key_ref: Automatically defines the KeyedRef::upcast_item_ref function using the covariance of the KeyRef<'a> type with regards to 'a.
simple_collection_mut: Automatically defines the CollectionMut::upcast_item_mut function using the covariance of the ItemMut<'a> type with regards to 'a.
simple_collection_ref: Automatically defines the SimpleCollectionRef::into_ref function.
simple_keyed_ref: Automatically defines the SimpleKeyedRef::into_ref function.

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.
CapacityMut: Collection with mutable capacity.
Clear: Clearable collection.
Collection: Abstract collection.
CollectionMut: Abstract collection that can be mutably referenced.
CollectionRef: Abstract collection that can be immutably referenced.
Deque: Immutable double-ended queue.
DequeMut: Mutable double-ended queue.
Front: Collection exposing a reference to its front element.
FrontMut: Collection exposing a mutable reference to its front element.
Get: Queryable collection.
GetKeyValue: Queryable map.
GetKeyValueMut: Mutably queryable map.
GetMut: Mutably queryable collection.
Insert: Mutable collection where new elements can be inserted.
Iter: Iterable collection.
IterMut: Mutably iterable collection.
Keyed: Abstract keyed collection.
KeyedRef: Abstract keyed collection whose key can be referenced.
Len: Sized collection.
Map: Imutable map data structure.
MapInsert: Mutable map where new new key-value pairs can be inserted.
MapIter
MapIterMut
MapMut: Mutable map data structure.
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.
Set: Imutable set data structure.
SetMut: Mutable set data structure.
SimpleCollectionMut: Collection where each item reference can be converted into a standard “simple” rust reference.
SimpleCollectionRef: Collection where each item reference can be converted into a standard “simple” rust reference.
SimpleKeyedRef: Keyed collection where each key reference can be converted into a standard “simple” rust reference.
Slab: Imutable slab data structure.
SlabMut: Mutable slab data structure.
Stack: Immutable stack data structure.
StackMut: Mutable stack data structure.
Vec: Immutable array data structure (conventionally nammed “Vec”).
VecDeque: Immutable indexable deque.
VecDequeMut: Mutable indexable deque.
VecMut: Mutable Vec data structure.
WithCapacity: Collection that can be created with a minimum given capacity.