Trait frunk_core::hlist::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");

Object Safety

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 = _