vendor/generic-array/README.md

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   3 # generic-array
   4
   5 This crate implements generic array types for Rust.
   6
   7 **Requires minumum Rust version of 1.36.0, or 1.41.0 for `From<[T; N]>` implementations**
   8
   9 [Documentation](http://fizyk20.github.io/generic-array/generic_array/)
  10
  11 ## Usage
  12
  13 The Rust arrays `[T; N]` are problematic in that they can't be used generically with respect to `N`, so for example this won't work:
  14
  15 ```rust
  16 struct Foo<N> {
  17         data: [i32; N]
  18 }
  19 ```
  20
  21 **generic-array** defines a new trait `ArrayLength<T>` and a struct `GenericArray<T, N: ArrayLength<T>>`, which let the above be implemented as:
  22
  23 ```rust
  24 struct Foo<N: ArrayLength<i32>> {
  25         data: GenericArray<i32, N>
  26 }
  27 ```
  28
  29 The `ArrayLength<T>` trait is implemented by default for [unsigned integer types](http://fizyk20.github.io/generic-array/typenum/uint/index.html) from [typenum](http://fizyk20.github.io/generic-array/typenum/index.html) crate:
  30
  31 ```rust
  32 use generic_array::typenum::U5;
  33
  34 struct Foo<N: ArrayLength<i32>> {
  35     data: GenericArray<i32, N>
  36 }
  37
  38 fn main() {
  39     let foo = Foo::<U5>{data: GenericArray::default()};
  40 }
  41 ```
  42
  43 For example, `GenericArray<T, U5>` would work almost like `[T; 5]`:
  44
  45 ```rust
  46 use generic_array::typenum::U5;
  47
  48 struct Foo<T, N: ArrayLength<T>> {
  49     data: GenericArray<T, N>
  50 }
  51
  52 fn main() {
  53     let foo = Foo::<i32, U5>{data: GenericArray::default()};
  54 }
  55 ```
  56
  57 In version 0.1.1 an `arr!` macro was introduced, allowing for creation of arrays as shown below:
  58
  59 ```rust
  60 let array = arr![u32; 1, 2, 3];
  61 assert_eq!(array[2], 3);
  62 ```