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

#[macro_use]
extern crate frunk;

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![|i, acc| i + acc,
                   |_, acc| if acc > 42f32 { 9000 } else { 0 },
                   |f, acc| 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]);

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.