Trait frunk_core::hlist::HFoldLeftable[][src]

pub trait HFoldLeftable<Folder, Acc> {
    type Output;
    fn foldl(self, folder: Folder, acc: Acc) -> Self::Output;
Expand description

Trait for performing a left fold over an HList

This trait is part of the implementation of the inherent method HCons::foldl. Please see that method for more information.

You only need to import this trait when working with generic HLists or Mappers of unknown type. If the type of everything is known, then list.foldl(f, acc) should “just work” even without the trait.

Associated Types

Required methods

Perform a left fold over an HList.

Please see the inherent method for more information.

The only difference between that inherent method and this trait method is the location of the type parameters. (here, they are on the trait rather than the method)


Implementation for folding over an HList using a single function that can handle all cases

let h = hlist![1, 2, 3, 4, 5];

let r: isize = h.foldl(|acc, next| acc + next, 0);
assert_eq!(r, 15);