Monocle.Iso

An Iso is a tool which converts elements of type A into elements of type B and back without loss.

Definition

type alias Iso a b =

{ get : a -> b

, reverseGet : b -> a

}

In order to create an Iso we need to supply two total functions: get and reverseGet

Laws

Identity:  \x -> iso.get(iso.reverseGet x) == x
Reversed:  \x -> iso.reverseGet(iso.get x) == x

Example

string2CharListIso : Iso String (List Char)
string2CharListIso =
    Iso String.toList String.fromList


(string2CharListIso.get "ABcdE") == ['A','B','c','d','E']
(string2CharListIso.reverseGet ['A','B','c','d','E']) == "ABcdE"

Derived methods

reverse : Iso a b -> Iso b a

Creates reversed Iso b a, exchanges functions get and reverseGet

    .get (Iso.reversed someiso) == someiso.reverseGet
    .reverseGet (Iso.reversed someiso) == someiso.get
    Iso.compose someiso (Iso.reversed someiso) == Iso identity identity

modify : Iso a b -> (b -> b) -> a -> a

Modifies given function (b -> b) to be (a -> a) using Iso a b

    someiso = Iso String.toList String.fromList
    somefx xs =  '@' :: xs
    modified = Iso.modify someiso somefx
    (modified "artur") == "@artur"

compose : Iso a b -> Iso b c -> Iso a c

Composes Iso a b with Iso b c and returns Iso a c

arturopala/elm-monocle/1.5.0

Monocle.Iso

Definition

Laws

Example

Derived methods

Modules