# [−][src]Module frunk::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]);Run

## Structs

HCons | Represents the most basic non-empty HList. Its value is held in |

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 |

IntoTuple2 | Trait for transforming an HList into a nested tuple. |

LiftFrom | Indexed type conversions of |

LiftInto | An indexed conversion that consumes |

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 |