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Basic optics: lenses, prisms, and traversals


Basic optics: lenses, prisms, and traversals

Lenses are becoming an increasingly important part of a Haskeller’s toolkit. Yet, when first approaching them, people may feel buried under a myriad of different lens-like thingies, and the complexity of some of the libraries implementing those concepts, like lens.

The goal of this talk is to provide a conceptual overview of three of the most important kinds of optics, namely lenses, prisms, and traversals. For most data types, those optics can be automatically generated, something we shall discuss. Finally, we shall look at one useful application of optics: treating semi-structured data such as JSON documents.

Haskell Course

If you liked this talk, you may consider joining us for Aleandro’s two-day intensive course on Haskell Fundamentals. The next public training course of this class runs July 6th - 7th, 2020 and has limited spots remaining.

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Company and Private Group Training


Alejandro Serrano

Alejandro Serrano

Lead Software Engineer


  • Optics
  • Haskell
  • Lenses
  • Prisms
  • Traversals
  • Records

This Talk includes:

  • Q&A session
  • Access to slides
  • Access to Academy Slack


  • Basic knowledge of Haskell
  • algebraic data types
  • pattern matching
  • type classes

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