Foldable

public protocol Foldable

Foldable describes types that have the ability to be folded to a summary value.

  • Eagerly folds a value to a summary value from left to right.

    Declaration

    Swift

    static func foldLeft<A, B>(_ fa: Kind<Self, A>, _ b: B, _ f: @escaping (B, A) -> B) -> B

    Parameters

    fa

    Value to be folded.

    b

    Initial value for the folding process.

    f

    Folding function.

    Return Value

    Summary value resulting from the folding process.

  • Lazily folds a value to a summary value from right to left.

    Declaration

    Swift

    static func foldRight<A, B>(_ fa: Kind<Self, A>, _ b: Eval<B>, _ f: @escaping (A, Eval<B>) -> Eval<B>) -> Eval<B>

    Parameters

    fa

    Value to be folded.

    b

    Initial value for the folding process.

    f

    Folding function.

    Return Value

    Summary value resulting from the folding process.

  • fold(_:) Extension method

    Folds a structure of values provided that its type has an instance of Monoid.

    It uses the monoid empty value as initial value and the combination method for the fold.

    Declaration

    Swift

    static func fold<A>(_ fa: Kind<Self, A>) -> A where A : Monoid

    Parameters

    fa

    Value to be folded.

    Return Value

    Summary value resulting from the folding process.

  • Reduces the elements of a structure down to a single value by applying the provided transformation and aggregation funtions in a left-associative manner.

    Declaration

    Swift

    static func reduceLeftToOption<A, B>(_ fa: Kind<Self, A>, _ f: @escaping (A) -> B, _ g: @escaping (B, A) -> B) -> Option<B>

    Parameters

    fa

    Value to be folded.

    f

    Transforming function.

    g

    Folding function.

    Return Value

    Optional summary value resulting from the folding process. It will be an Option.none if the structure is empty, or a value if not.

  • Reduces the elements of a structure down to a single value by applying the provided transformation and aggregation functions in a right-associative manner.

    Declaration

    Swift

    static func reduceRightToOption<A, B>(_ fa: Kind<Self, A>, _ f: @escaping (A) -> B, _ g: @escaping (A, Eval<B>) -> Eval<B>) -> Eval<Option<B>>

    Parameters

    fa

    Value to be folded.

    f

    Transforming function.

    g

    Folding function.

    Return Value

    Optional summary value resulting from the folding process. It will be an Option.none if the structure is empty, or a value if not.

  • reduceLeftOption(_:_:) Extension method

    Reduces the elements of a structure down to a single value by applying the provided aggregation function in a left-associative manner.

    Declaration

    Swift

    static func reduceLeftOption<A>(_ fa: Kind<Self, A>, _ f: @escaping (A, A) -> A) -> Option<A>

    Parameters

    fa

    Value to be folded.

    f

    Folding function.

    Return Value

    Optional summary value resulting from the folding process.

  • reduceRightOption(_:_:) Extension method

    Reduces the elements of a structure down to a single value by applying the provided aggregation function in a right-associative manner.

    Declaration

    Swift

    static func reduceRightOption<A>(_ fa: Kind<Self, A>, _ f: @escaping (A, Eval<A>) -> Eval<A>) -> Eval<Option<A>>

    Parameters

    fa

    Value to be folded.

    f

    Folding function.

    Return Value

    Optional summary value resulting from the folding process.

  • combineAll(_:) Extension method

    Folds a structure of values provided that its type has an instance of Monoid.

    It uses the monoid empty value as initial value and the combination method for the fold.

    Declaration

    Swift

    static func combineAll<A>(_ fa: Kind<Self, A>) -> A where A : Monoid

    Parameters

    fa

    Value to be folded.

    Return Value

    Summary value resulting from the folding process.

  • foldMap(_:_:) Extension method

    Transforms the elements of a structure to a type with a Monoid instance and folds them using the empty and combine methods of such Monoid instance.

    Declaration

    Swift

    static func foldMap<A, B: Monoid>(_ fa: Kind<Self, A>, _ f: @escaping (A) -> B) -> B

    Parameters

    fa

    Value to be transformed and folded.

    f

    Transforming function.

    Return Value

    Summary value resulting from the transformation and folding process.

  • traverse_(_:_:) Extension method

    Traverses a structure of values, transforming them with a provided function and discarding the result of its effect.

    Declaration

    Swift

    static func traverse_<G: Applicative, A, B>(_ fa: Kind<Self, A>, _ f: @escaping (A) -> Kind<G, B>) -> Kind<G, Unit>

    Parameters

    fa

    Structure of values.

    f

    Transforming function.

    Return Value

    Unit in the context of the effect of the result of the transforming function.

  • sequence_(_:) Extension method

    Traverses a structure of effects, performing them and discarding their result.

    Declaration

    Swift

    static func sequence_<G, A>(_ fga: Kind<Self, Kind<G, A>>) -> Kind<G, Unit> where G : Applicative

    Parameters

    fga

    Structure of effects.

    Return Value

    Unit in the context of the effects contained in the structure.

  • find(_:_:) Extension method

    Looks for an element that matches a given predicate.

    Declaration

    Swift

    static func find<A>(_ fa: Kind<Self, A>, _ f: @escaping (A) -> Bool) -> Option<A>

    Parameters

    fa

    Structure of values where the element matching the predicate needs to be found.

    f

    Predicate.

    Return Value

    A value if there is any that matches the predicate, or Option.none.

  • exists(_:_:) Extension method

    Checks if any element in a structure matches a given predicate.

    Declaration

    Swift

    static func exists<A>(_ fa: Kind<Self, A>, _ predicate: @escaping (A) -> Bool) -> Bool

    Parameters

    fa

    Structure of values where the element matching the predicate needs to be found.

    predicate

    Predicate.

    Return Value

    A boolean value indicating if any elements in the structure match the predicate.

  • forall(_:_:) Extension method

    Checks if all elements in a structure match a given predicate.

    Declaration

    Swift

    static func forall<A>(_ fa: Kind<Self, A>, _ predicate: @escaping (A) -> Bool) -> Bool

    Parameters

    fa

    Structure of values where all elements should match the predicate.

    predicate

    Predicate.

    Return Value

    A boolean value indicating if all elements in the structure match the predicate.

  • isEmpty(_:) Extension method

    Checks if a structure of values is empty.

    Declaration

    Swift

    static func isEmpty<A>(_ fa: Kind<Self, A>) -> Bool

    Parameters

    fa

    Structure of values.

    Return Value

    false if the structure contains any value, true otherwise.

  • nonEmpty(_:) Extension method

    Checks if a structure of values is not empty.

    Declaration

    Swift

    static func nonEmpty<A>(_ fa: Kind<Self, A>) -> Bool

    Parameters

    fa

    Structure of values.

    Return Value

    true if the structure contains any value, false otherwise.

  • foldM(_:_:_:) Extension method

    Performs a monadic left fold from the source context to the target monad.

    Declaration

    Swift

    static func foldM<G: Monad, A, B>(_ fa: Kind<Self, A>, _ b: B, _ f: @escaping (B, A) -> Kind<G, B>) -> Kind<G, B>

    Parameters

    fa

    Structure of values.

    b

    Initial value for the fold.

    f

    Folding function.

    Return Value

    Summary value resulting from the folding process in the context of the target monad.

  • foldMapM(_:_:) Extension method

    Performs a monadic left fold by mapping the values in a structure to ones in the target monad context and using the Monoid instance to combine them.

    Declaration

    Swift

    static func foldMapM<G: Monad, A, B: Monoid>(_ fa: Kind<Self, A>, _ f: @escaping (A) -> Kind<G, B>) -> Kind<G, B>

    Parameters

    fa

    Structure of values.

    f

    Trasnforming function.

    Return Value

    Summary value resulting from the transformation and folding process in the context of the target monad.

  • get(_:_:) Extension method

    Obtains a specific element of a structure of elements given its indexed position.

    Declaration

    Swift

    static func get<A>(_ fa: Kind<Self, A>, _ index: Int64) -> Option<A>

    Parameters

    fa

    Structure of values.

    index

    Indexed position of the element to retrieve.

    Return Value

    A value if there is any at the given position, or Option.none otherwise.

  • count(_:) Extension method

    Counts how many elements a structure contains.

    Declaration

    Swift

    static func count<A>(_ fa: Kind<Self, A>) -> Int64

    Parameters

    fa

    Structure of values.

    Return Value

    An integer value with the count of how many elements are contained in the structure.