Foldable

Lean: Hale.Base.Foldable | Haskell: Data.Foldable

Overview

Typeclass for structures that can be folded to a summary value. Provides a rich API with many derived operations built on top of foldr.

API Mapping

Lean	Haskell	Kind
`Foldable` class	`Foldable`	Typeclass
`foldr`	`foldr`	Method
`foldl`	`foldl'`	Method
`toList`	`toList`	Method
`foldMap`	`foldMap`	Function
`null`	`null`	Function
`length`	`length`	Function
`any`	`any`	Function
`all`	`all`	Function
`find?`	`find`	Function
`elem`	`elem`	Function
`minimum?`	`minimum`	Function
`maximum?`	`maximum`	Function
`sum`	`sum`	Function
`product`	`product`	Function

Instances

Foldable List
Foldable Option
Foldable List.NonEmpty
Foldable (Either a)

Proofs & Guarantees

None listed (correctness follows from typeclass laws).

Example

-- Sum all elements in a list
Foldable.sum [1, 2, 3]
-- => 6