Trait HList

pub trait HList: Sized {
    const LEN: usize;

    // Required method
    fn static_len() -> usize;

    // Provided methods
    fn len(&self) -> usize { ... }
    fn is_empty(&self) -> bool { ... }
    fn prepend<H>(self, h: H) -> HCons<H, Self> { ... }
}

Typeclass for HList-y behaviour

An HList is a heterogeneous list, one that is statically typed at compile time. In simple terms, it is just an arbitrarily-nested Tuple2.

Required Associated Constants

const LEN: usize

Returns the length of a given HList type without making use of any references, or in fact, any values at all.

Examples

use frunk::prelude::*;
use frunk_core::HList;

assert_eq!(<HList![i32, bool, f32]>::LEN, 3);

Required Methods

fn static_len() -> usize

👎Deprecated since 0.1.31: Please use LEN instead

Returns the length of a given HList type without making use of any references, or in fact, any values at all.

Examples

use frunk::prelude::*;
use frunk_core::HList;

assert_eq!(<HList![i32, bool, f32]>::static_len(), 3);

Provided Methods

fn len(&self) -> usize

Returns the length of a given HList

Examples

use frunk_core::hlist;

let h = hlist![1, "hi"];
assert_eq!(h.len(), 2);

fn is_empty(&self) -> bool

Returns whether a given HList is empty

Examples

use frunk_core::hlist;

let h = hlist![];
assert!(h.is_empty());

fn prepend<H>(self, h: H) -> HCons<H, Self>

Prepends an item to the current HList

Examples

use frunk_core::hlist;

let h1 = hlist![1, "hi"];
let h2 = h1.prepend(true);
let (a, (b, c)) = h2.into_tuple2();
assert_eq!(a, true);
assert_eq!(b, 1);
assert_eq!(c, "hi");

Dyn Compatibility

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety", so this trait is not object safe.

Implementors

impl HList for HNil

const LEN: usize = 0usize

impl<H, T: HList> HList for HCons<H, T>

const LEN: usize