Lightning - Monads you already use (without knowing it)

Transcript

1. Monads you’ve already put in prod Tejas Dinkar Nilenso Software

2. about.me • Hi, I’m Tejas • Nilenso: Partner • twitter:

   tdinkar • github: gja

3. If you think you understand Monads, you don't understand Monads.

4. This talk is inaccurate and will make a mathematician cry

5. Monads • Programmable Semicolons • Used to hide plumbing away

   from you • Monads are just monoids in the category of endofunctors
6. None

7. Values Value

8. Monads Value Box

9. Monads • Monads define two functions • return takes a

   value and puts it in a box • bind takes a box & function, and returns a box with f(value)

10. Some math (√4) + 5

11. Some math (√4) + 5 3 or 7!

12. Value 4

13. Monad [4]

14. return def m_return(x) [x] end # m_r(4) => [4]

15. Square Root fn def sqrt(x) s = Math.sqrt(x) [s, -s]

    end # sqrt(4) => [2, -2]

16. Bind Function x = m_return(4) y = ?????(x) { |p|

    sqrt(p) } # I want [-2, 2]

17. Bind Function x = m_return(4) y = x.flat_map {|p| sqrt(p)

    } # y => [2, -2]

18. Increment Fn def inc_5(x) [x + 5] end # inc_5(1)

    => [6]

19. Putting it together m_return(4). flat_map {|p| sqrt(p)}. flat_map {|p| inc_5(p)}

    # => [3, 7]

20. You have invented the List Monad, used to model non-determinism

    Congrats