Module frunk_core::hlist

Module that holds HList data structures, implementations, and typeclasses.

Typically, you would want to use the hlist! macro to make it easier for you to use HList.

Examples

use frunk_core::{hlist, HList, poly_fn};

let h = hlist![1, "hi"];
assert_eq!(h.len(), 2);
let (a, b) = h.into_tuple2();
assert_eq!(a, 1);
assert_eq!(b, "hi");

// Reverse
let h1 = hlist![true, "hi"];
assert_eq!(h1.into_reverse(), hlist!["hi", true]);

// foldr (foldl also available)
let h2 = hlist![1, false, 42f32];
let folded = h2.foldr(
            hlist![|acc, i| i + acc,
                   |acc, _| if acc > 42f32 { 9000 } else { 0 },
                   |acc, f| f + acc],
            1f32
    );
assert_eq!(folded, 9001);

let h3 = hlist![9000, "joe", 41f32];
// Mapping over an HList with a polymorphic function,
// declared using the poly_fn! macro (you can choose to impl
// it manually)
let mapped = h3.map(
  poly_fn![
    |f: f32|   -> f32 { f + 1f32 },
    |i: isize| -> isize { i + 1 },
    ['a] |s: &'a str| -> &'a str { s }
  ]);
assert_eq!(mapped, hlist![9001, "joe", 42f32]);

// Plucking a value out by type
let h4 = hlist![1, "hello", true, 42f32];
let (t, remainder): (bool, _) = h4.pluck();
assert!(t);
assert_eq!(remainder, hlist![1, "hello", 42f32]);

// Resculpting an HList
let h5 = hlist![9000, "joe", 41f32, true];
let (reshaped, remainder2): (HList![f32, i32, &str], _) = h5.sculpt();
assert_eq!(reshaped, hlist![41f32, 9000, "joe"]);
assert_eq!(remainder2, hlist![true]);

Modules

• foldr_owned
  HFoldRightable inner mechanics for folding with a folder that needs to be owned.

Structs

• HCons
  Represents the most basic non-empty HList. Its value is held in head while its tail is another HList.
• HNil
  Represents the right-most end of a heterogeneous list

Traits

• HFoldLeftable
  Trait for performing a left fold over an HList
• HFoldRightable
  Trait for performing a right fold over an HList
• HList
  Typeclass for HList-y behaviour
• HMappable
  Trait for mapping over an HList
• HZippable
  Trait for zipping HLists
• IntoTuple2
  Trait for transforming an HList into a nested tuple.
• LiftFrom
  Indexed type conversions of T -> Self with index I. This is a generalized version of From which for example allows the caller to use default values for parts of Self and thus “fill in the blanks”.
• LiftInto
  An indexed conversion that consumes self, and produces a T. To produce T, the index I may be used to for example “fill in the blanks”. LiftInto is the reciprocal of LiftFrom.
• Plucker
  Trait defining extraction from a given HList
• Sculptor
  Trait for pulling out some subset of an HList, using type inference.
• Selector
  Trait for borrowing an HList element by type

Functions

• h_cons
  Takes an element and an Hlist and returns another one with the element prepended to the original list. The original list is consumed
• lift_from
  Free function version of LiftFrom::lift_from.