[−][src]Trait core_extensions::ConstDefault

pub trait ConstDefault: Sized {
    pub const DEFAULT: Self;
}

A const equivalent of the Default trait.

Features

Enabling the "const_generics" feature allows arrays of all lengths to implement this trait, otherwise it's only implemented for arrays up to 32 elements long.

Example

Implementing ConstDefault for a struct

// use core_extensions::const_default; // in newer versions of Rust.
#[macro_use(const_default)]
extern crate core_extensions;

use core_extensions::ConstDefault;
 
#[derive(Debug,PartialEq)]
struct Point<T>{
    x:T,
    y:T,
}

// `+ Copy` here is required for Rust 1.20 and 1.21,
// and can be removed from Rust 1.22 onwards.
impl<T> ConstDefault for Point<T>
where
    T: ConstDefault + Copy
{
    const DEFAULT: Self= Point{ x: T::DEFAULT,  y: T::DEFAULT };
}

assert_eq!( const_default!(Point<u8>), Point{x:0, y:0} );
assert_eq!( const_default!(Point<f32>), Point{x:0.0, y:0.0} );
assert_eq!( const_default!(Point<Option<()>>), Point{x:None, y:None} );

Associated Constants

`pub const DEFAULT: Self`[src]

The default value for Self.

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Implementations on Foreign Types

`impl<T: ConstDefault, const N: usize> ConstDefault for [T; N]`[src]

This is supported on crate feature const_params only.

When the "const_params" feature is disabled, the ConstDefault trait is implemented for arrays up to 32 elements long.

`pub const DEFAULT: Self`[src]

`impl ConstDefault for ()`[src]

`pub const DEFAULT: Self`[src]

`impl<A> ConstDefault for (A,) where A: ConstDefault + Sized,` [src]

`pub const DEFAULT: Self`[src]

`impl<A, B> ConstDefault for (A, B) where A: ConstDefault + Sized, B: ConstDefault + Sized,` [src]

`pub const DEFAULT: Self`[src]

`impl<A, B, C> ConstDefault for (A, B, C) where A: ConstDefault + Sized, B: ConstDefault + Sized, C: ConstDefault + Sized,` [src]

`pub const DEFAULT: Self`[src]

`impl<A, B, C, D> ConstDefault for (A, B, C, D) where A: ConstDefault + Sized, B: ConstDefault + Sized, C: ConstDefault + Sized, D: ConstDefault + Sized,` [src]

`pub const DEFAULT: Self`[src]

`impl<A, B, C, D, E> ConstDefault for (A, B, C, D, E) where A: ConstDefault + Sized, B: ConstDefault + Sized, C: ConstDefault + Sized, D: ConstDefault + Sized, E: ConstDefault + Sized,` [src]

`pub const DEFAULT: Self`[src]

`impl<A, B, C, D, E, F> ConstDefault for (A, B, C, D, E, F) where A: ConstDefault + Sized, B: ConstDefault + Sized, C: ConstDefault + Sized, D: ConstDefault + Sized, E: ConstDefault + Sized, F: ConstDefault + Sized,` [src]

`pub const DEFAULT: Self`[src]

`impl<A, B, C, D, E, F, G> ConstDefault for (A, B, C, D, E, F, G) where A: ConstDefault + Sized, B: ConstDefault + Sized, C: ConstDefault + Sized, D: ConstDefault + Sized, E: ConstDefault + Sized, F: ConstDefault + Sized, G: ConstDefault + Sized,` [src]

`pub const DEFAULT: Self`[src]

`impl<A, B, C, D, E, F, G, H> ConstDefault for (A, B, C, D, E, F, G, H) where A: ConstDefault + Sized, B: ConstDefault + Sized, C: ConstDefault + Sized, D: ConstDefault + Sized, E: ConstDefault + Sized, F: ConstDefault + Sized, G: ConstDefault + Sized, H: ConstDefault + Sized,` [src]

`pub const DEFAULT: Self`[src]

`impl<A, B, C, D, E, F, G, H, I> ConstDefault for (A, B, C, D, E, F, G, H, I) where A: ConstDefault + Sized, B: ConstDefault + Sized, C: ConstDefault + Sized, D: ConstDefault + Sized, E: ConstDefault + Sized, F: ConstDefault + Sized, G: ConstDefault + Sized, H: ConstDefault + Sized, I: ConstDefault + Sized,` [src]

`pub const DEFAULT: Self`[src]

`impl<A, B, C, D, E, F, G, H, I, J> ConstDefault for (A, B, C, D, E, F, G, H, I, J) where A: ConstDefault + Sized, B: ConstDefault + Sized, C: ConstDefault + Sized, D: ConstDefault + Sized, E: ConstDefault + Sized, F: ConstDefault + Sized, G: ConstDefault + Sized, H: ConstDefault + Sized, I: ConstDefault + Sized, J: ConstDefault + Sized,` [src]

`pub const DEFAULT: Self`[src]

`impl<A, B, C, D, E, F, G, H, I, J, K> ConstDefault for (A, B, C, D, E, F, G, H, I, J, K) where A: ConstDefault + Sized, B: ConstDefault + Sized, C: ConstDefault + Sized, D: ConstDefault + Sized, E: ConstDefault + Sized, F: ConstDefault + Sized, G: ConstDefault + Sized, H: ConstDefault + Sized, I: ConstDefault + Sized, J: ConstDefault + Sized, K: ConstDefault + Sized,` [src]

`pub const DEFAULT: Self`[src]

`impl<A, B, C, D, E, F, G, H, I, J, K, L> ConstDefault for (A, B, C, D, E, F, G, H, I, J, K, L) where A: ConstDefault + Sized, B: ConstDefault + Sized, C: ConstDefault + Sized, D: ConstDefault + Sized, E: ConstDefault + Sized, F: ConstDefault + Sized, G: ConstDefault + Sized, H: ConstDefault + Sized, I: ConstDefault + Sized, J: ConstDefault + Sized, K: ConstDefault + Sized, L: ConstDefault + Sized,` [src]

`pub const DEFAULT: Self`[src]

impl<A, B, C, D, E, F, G, H, I, J, K, L, M> ConstDefault for (A, B, C, D, E, F, G, H, I, J, K, L, M) where A: ConstDefault + Sized, B: ConstDefault + Sized, C: ConstDefault + Sized, D: ConstDefault + Sized, E: ConstDefault + Sized, F: ConstDefault + Sized, G: ConstDefault + Sized, H: ConstDefault + Sized, I: ConstDefault + Sized, J: ConstDefault + Sized, K: ConstDefault + Sized, L: ConstDefault + Sized, M: ConstDefault + Sized, [src]

`pub const DEFAULT: Self`[src]

impl<A, B, C, D, E, F, G, H, I, J, K, L, M, N> ConstDefault for (A, B, C, D, E, F, G, H, I, J, K, L, M, N) where A: ConstDefault + Sized, B: ConstDefault + Sized, C: ConstDefault + Sized, D: ConstDefault + Sized, E: ConstDefault + Sized, F: ConstDefault + Sized, G: ConstDefault + Sized, H: ConstDefault + Sized, I: ConstDefault + Sized, J: ConstDefault + Sized, K: ConstDefault + Sized, L: ConstDefault + Sized, M: ConstDefault + Sized, N: ConstDefault + Sized, [src]

`pub const DEFAULT: Self`[src]

impl<A, B, C, D, E, F, G, H, I, J, K, L, M, N, O> ConstDefault for (A, B, C, D, E, F, G, H, I, J, K, L, M, N, O) where A: ConstDefault + Sized, B: ConstDefault + Sized, C: ConstDefault + Sized, D: ConstDefault + Sized, E: ConstDefault + Sized, F: ConstDefault + Sized, G: ConstDefault + Sized, H: ConstDefault + Sized, I: ConstDefault + Sized, J: ConstDefault + Sized, K: ConstDefault + Sized, L: ConstDefault + Sized, M: ConstDefault + Sized, N: ConstDefault + Sized, O: ConstDefault + Sized, [src]

`pub const DEFAULT: Self`[src]

impl<A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P> ConstDefault for (A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P) where A: ConstDefault + Sized, B: ConstDefault + Sized, C: ConstDefault + Sized, D: ConstDefault + Sized, E: ConstDefault + Sized, F: ConstDefault + Sized, G: ConstDefault + Sized, H: ConstDefault + Sized, I: ConstDefault + Sized, J: ConstDefault + Sized, K: ConstDefault + Sized, L: ConstDefault + Sized, M: ConstDefault + Sized, N: ConstDefault + Sized, O: ConstDefault + Sized, P: ConstDefault + Sized, [src]

`pub const DEFAULT: Self`[src]

`impl ConstDefault for i8`[src]

`pub const DEFAULT: Self`[src]

`impl ConstDefault for u8`[src]

`pub const DEFAULT: Self`[src]

`impl ConstDefault for i16`[src]

`pub const DEFAULT: Self`[src]

`impl ConstDefault for u16`[src]

`pub const DEFAULT: Self`[src]

`impl ConstDefault for i32`[src]

`pub const DEFAULT: Self`[src]

`impl ConstDefault for u32`[src]

`pub const DEFAULT: Self`[src]

`impl ConstDefault for i64`[src]

`pub const DEFAULT: Self`[src]

`impl ConstDefault for u64`[src]

`pub const DEFAULT: Self`[src]

`impl ConstDefault for f32`[src]

`pub const DEFAULT: Self`[src]

`impl ConstDefault for f64`[src]

`pub const DEFAULT: Self`[src]

`impl ConstDefault for bool`[src]

`pub const DEFAULT: Self`[src]

`impl ConstDefault for char`[src]

`pub const DEFAULT: Self`[src]

`impl<T: ?Sized> ConstDefault for PhantomData<T>`[src]

`pub const DEFAULT: Self`[src]

`impl<T> ConstDefault for Option<T>`[src]

`pub const DEFAULT: Self`[src]

`impl<'a> ConstDefault for &'a str`[src]

`pub const DEFAULT: Self`[src]

`impl<'a, T: 'a> ConstDefault for &'a [T]`[src]

`pub const DEFAULT: Self`[src]

`impl<T: ConstDefault> ConstDefault for Wrapping<T>`[src]

`pub const DEFAULT: Self`[src]

`impl<T: ConstDefault> ConstDefault for Reverse<T>`[src]

`pub const DEFAULT: Self`[src]

`impl ConstDefault for AtomicUsize`[src]

`pub const DEFAULT: Self`[src]

`impl ConstDefault for AtomicIsize`[src]

`pub const DEFAULT: Self`[src]

`impl ConstDefault for AtomicBool`[src]

`pub const DEFAULT: Self`[src]

`impl<T: ConstDefault> ConstDefault for Cell<T>`[src]

`pub const DEFAULT: Self`[src]

`impl<T: ConstDefault> ConstDefault for RefCell<T>`[src]

`pub const DEFAULT: Self`[src]

`impl<T: ConstDefault> ConstDefault for UnsafeCell<T>`[src]

`pub const DEFAULT: Self`[src]

`impl ConstDefault for Duration`[src]

`pub const DEFAULT: Self`[src]

`impl ConstDefault for i128`[src]

`pub const DEFAULT: Self`[src]

`impl ConstDefault for u128`[src]

`pub const DEFAULT: Self`[src]

`impl<T: ConstDefault> ConstDefault for ManuallyDrop<T>`[src]

`pub const DEFAULT: Self`[src]

`impl ConstDefault for AtomicI8`[src]

`pub const DEFAULT: Self`[src]

`impl ConstDefault for AtomicU8`[src]

`pub const DEFAULT: Self`[src]

`impl ConstDefault for AtomicI16`[src]

`pub const DEFAULT: Self`[src]

`impl ConstDefault for AtomicU16`[src]

`pub const DEFAULT: Self`[src]

`impl ConstDefault for AtomicI32`[src]

`pub const DEFAULT: Self`[src]

`impl ConstDefault for AtomicU32`[src]

`pub const DEFAULT: Self`[src]

`impl ConstDefault for AtomicI64`[src]

`pub const DEFAULT: Self`[src]

`impl ConstDefault for AtomicU64`[src]

`pub const DEFAULT: Self`[src]

`impl<T> ConstDefault for Vec<T>`[src]

`pub const DEFAULT: Self`[src]

`impl ConstDefault for String`[src]

`pub const DEFAULT: Self`[src]

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Implementors

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