Boxed.Lst

A couple of well known tools carried over from the List module, and others derived from it. Since the members of a list are Boxed, all of them can be encapsulations of values of different types.

Unboxing

mapHead : (Boxed c -> Maybe a) -> Boxed c -> Maybe a

Returns the first member of a boxed list, only if it could be transformed into a different value.

mapHead asInt (Lst [ Integer 1, Str "b", Double 3.01 ]) == Just 1




--It was decided that integers can become floats
mapHead asFloat (Lst [ Integer 1, Str "b", Double 3.01 ]) == Just 1


mapHead asString (Lst [ Integer 1, Str "b", Double 3.01 ]) == Nothing

mapFind : (Boxed c -> Maybe a) -> Boxed c -> Maybe a

Finds a member in a boxed list, only if it could be transformed into a different value.

mapFind asString (Lst [ Integer 1, Str "b", Double 3.01 ]) == Just "b"


mapFind asBool (Lst [ Integer 1, Str "b", Double 3.01 ]) == Nothing

filterMap : (Boxed c -> Maybe a) -> Boxed c -> List a

Returns only succesful values, resulting from the application of a given function.

filterMap asFloat (Lst [ Integer 1, Str "b", Double 3.01 ]) == [ 1, 3.01 ]


filterMap asBool (Lst [ Integer 1, Str "b", Double 3.01 ]) == []


filterMap asBool (Double 3.01) == []

foldr : (Boxed c -> a -> a) -> a -> Boxed c -> a

Reduce a boxed list from the right.

foldl : (Boxed c -> a -> a) -> a -> Boxed c -> a

Reduce a boxed list from the left.

Putting Lists Together

cons : Boxed c -> Boxed c -> Boxed c

Adds an element to the front of a Boxed list. The encapsulated value of the new member does not need to be of the same type as the rest.

cons (Integer 1) (Lst [ Str "b", Double 3.03 ]) == Lst [ Integer 1, Str "b", Double 3.03 ]


cons (Integer 1) (Lst []) == Lst [ Integer 1 ]


cons (Integer 1) (Str "d") == Lst [ Integer 1 ]

Extraction

find : (Boxed c -> Bool) -> Boxed c -> Maybe (Boxed c)

Finds, inside a list, a 'Boxed' that passes a given test.

 find isString (Lst [Integer 1, Str "b", Double 3.01]) == Just (Str "b")
 find isTuple (Lst [Integer 1, Str "b", Double 3.01]) == Nothing
 find isNull (Lst [Integer 1, Null, Double 3.01]) == Just Null

Mapping

apply : (List (Boxed c) -> a) -> Boxed c -> a

Apply a given function to a boxed list.

apply List.head (Lst [ Integer 1, Str "b", Double 3.03 ]) == Just (Integer 1)


apply List.tail (Lst [ Integer 1, Str "b", Double 3.03 ]) == Just [ Str "b", Double 3.03 ]


apply (List.member (Str "b")) (Lst [ Integer 1, Str "b", Double 3.03 ]) == True


apply (List.map asInt) (Lst [ Integer 1, Str "b", Double 3.03 ]) == [ Just 1, Nothing, Nothing ]

bundsol/boxed/2.0.0

Boxed.Lst

Unboxing

Putting Lists Together

Extraction

Mapping

Modules