Lesson 3: Sequencing effects

  • Sequencing with effects
  • Revisiting Validation
    • Exercise 1
    • Exercise 1, Part 2
  • Discarding results
  • Parsing
    • Exercise 2
  • Coming up

Previously we looked at the connection between <*> and liftA2, their connection to fmap, the pure function, and the monoidal structure of applicatives. We will still want to give some closeup attention to a few other applicatives, especially functions and lists, but this lesson will focus on the other operators in the typeclass (<* and *>) before we move on to those. While you almost never need to implement them yourself – because the compiler can derive them from your implementations of pure and <*> (or pure and liftA2) – they are useful, yet often ignored. They are useful enough to deserve at least one lesson of their own.

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