Lenses: compositional data access and manipulation. | SkillsCast
9th October 2013 in London There are 6 other SkillsCasts available from Haskell eXchange 2013 Please log in to watch this conference skillscast. Haskell lets you write beautiful, modular code. Rather than waffle generally, I’ll use this talk to look at a particular example, Edward Kmett’s lovely lens library. Lenses have been called “jQuery for data types”: they give you a way to poke around in th
Lens Tutorial - Introduction (part 1) - Jakub Arnold Blog
Programování jako zábavná hra! Děti, ale i dospělí se mohou naučit kódovat velice přístupnou formou, která bude všechny bavit! Foto: Pixabay Základy programování Programování se může zdát jako složitá věda, ale s dnešními dostupnými nástroji se tomuto řemeslu může naučit každý. Samozřejmě záleží, jaké k tomu má kdo dispozice a kolik času je ochoten učení věnovat. Už ale dávno neplatí, že je progra
Pinholes - Idiomatic Clojure Lenses
Lenses are a construct for getting, "setting" or "modifying" values within data structures, especially deeply nested data structures. The quotation marks have the usual meaning when they show up in funktionsprache:1 not mutating anything per se, but instead producing an object, or reference thereto, that is identical except for the requested change. In Scala, the need for lenses is pretty glaring,
CPS based functional references
I have recently come up with a new way of representing functional references. As you might recall, functional references (also called lenses) are like a pointer into a field of some data structure. The value of this field can be extracted and modified. For example: GHCi> get fstF (123,"hey") 123 GHCi> set fstF 456 (123,"hey") (456,"hey") GHCi> modify fstF (*2) (123,"hey") (246,"hey") where fstF is
Lensことはじめ - あどけない話
見ろ！ Haskell が OOPL のようだ！ さてさて、ようやく重い腰を上げて、Lens を勉強し始めましたよ。Haksell for allを見て勉強すればいいのかなと思ったんですが、解説しているパッケージが data-lens なので古いですね。 今、使うべきなのは、lens というパッケージらしいです。解説は、この README を読むのが一番だそうです。この README と Haskell for all をにらめっこしながら、Lens の getter と setter の機能を使ってみます。 背景 Haskell の代数データ型にはフィールドラベルが定義できて、これがいわゆる getter と setter の役割を果たします。Haskell for all から例を引用してみましょう。 data Point = Point { x :: Double , y :: Do
A Little Lens Starter Tutorial - School of Haskell | School of Haskell
Interactive code snippets not yet available for SoH 2.0, see our Status of of School of Haskell 2.0 blog post What is lens?lens is a package which provides the type synonym Lens which is one of a few implementations of the concept of lenses, or functional references. lens also provides a number of generalizations of lenses including Prisms, Traversals, Isos, and Folds. Why do I care?Lenses and the
Lenses
Haskell's Lens type generalizes properties (i.e. accessors/mutators) found in other programming languages. For example, C# provides language support to treat properties as ordinary variables: class Point { public double x { get; set; } public double y { get; set; } } class Circle { public Point center { get; set; } public double radius { get; set; } } public void goRight(ref Circle c) { c.center.x
Lenses, Folds, and Traversals
Slides: http://comonad.com/haskell/Lenses-Folds-and-Traversals-NYC.pdf This was a talk I gave at the second New York Haskell User Group Meeting (http://www.meetup.com/NY-Haskell/) on the new lens library, which provides a highly composable toolbox for accessing and modifying multiple parts of data structures. Starting with building blocks such as fmap and (.), we build up combinators suitable fo
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