Const generics let Rust items accept compile-time constant values as generic parameters. Alongside type and lifetime generics, they form Rust’s third kind of generic parameter. They are especially useful for arrays, whose types include both an element type and a length. section 16.1 section 16.6
Const generics solve a common array-size problem:
- An [i32; 3] and an [i32; 4] are different types because their lengths differ. section 16.1
- Without const generics, separate structs and trait implementations may be needed for every supported array length. section 16.1
- With const N: usize, one definition can use [T; N] for many element types and array lengths. section 16.1
A buffer whose size is part of its type
struct Buffers<T, const N: usize> { array_one: [T; N], array_two: [T; N], } This single definition can create a three-element u8 buffer or a four-element i32 buffer. The compiler uses the supplied type and constant length to determine each concrete type. section 16.1
struct Buffers<T, const N: usize> {
array_one: [T; N],
array_two: [T; N]
}
Inspect the compact generic buffer definition using both a type parameter and a const length parameter. section 16.1
