vendor/generic-array-0.12.3/README.md

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   3 # generic-array
   4
   5 This crate implements generic array types for Rust.
   6
   7 [Documentation](http://fizyk20.github.io/generic-array/generic_array/)
   8
   9 ## Usage
  10
  11 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:
  12
  13 ```rust
  14 struct Foo<N> {
  15         data: [i32; N]
  16 }
  17 ```
  18
  19 **generic-array** defines a new trait `ArrayLength<T>` and a struct `GenericArray<T, N: ArrayLength<T>>`, which let the above be implemented as:
  20
  21 ```rust
  22 struct Foo<N: ArrayLength<i32>> {
  23         data: GenericArray<i32, N>
  24 }
  25 ```
  26
  27 To actually define a type implementing `ArrayLength`, you can use unsigned integer types defined in [typenum](https://github.com/paholg/typenum) crate - for example, `GenericArray<T, U5>` would work almost like `[T; 5]` :)
  28
  29 In version 0.1.1 an `arr!` macro was introduced, allowing for creation of arrays as shown below:
  30
  31 ```rust
  32 let array = arr![u32; 1, 2, 3];
  33 assert_eq!(array[2], 3);
  34 ```