Like bow ties and time travel, algebraic data types are really cool. They help you match the data model to your domain while still providing type safety. With the help of the Doctor and his traveling companions, this session will explore the universe of product types and sum types, helping you shape your app's data in a way that accurately reflects the domain you are working in and that improves the completeness of your code. And don't worry, you don't need to be a Time Lord to get started!

1. Algebraic Data Types
Are Cool

2. Sum Type

3. This OR That

4. Discriminated Union (Sum Type)
type Nemesis =
| Dalek
| Cyberman

5. Product Type

6. This AND That

7. Record (Product Type)
type Nemesises = // Nemesii? Nemeses?
{ Dalek : Nemesis
Cyberman : Nemesis }

8. So why are Algebraic Data Types so cool?
Expressive and flexible domain
modeling through types

9. type Doctor =
| Ninth
| Tenth
| Eleventh
| Twelfth
| Thirteenth
type Companion =
| RoseTyler
| MarthaJones
| AmyPond
| ClaraOswald
| BillPotts
| YasminKhan

10. type EpisodeIdentifier =
| Number of int
| Name of string

11. type DrWhoEpisode =
{ Doctor : Doctor
Companion : Companion
Identifier : EpisodeIdentifier }

12. So why are Algebraic Data Types so cool?
Linter/Intellisense warnings, to
ensure all components of an
algebraic data type are handled

13. let newEpisode =
{ Doctor = Twelfth
Companion = BillPotts
Identifier = (Name “Twice Upon a Time”) }

14. let newEpisode =
{ Doctor = Twelfth
Companion = BillPotts }

15. let newEpisode =
{ Doctor = Twelfth
Companion = BillPotts }

16. let wibblyWobbly episode =
match episode.Identifier with
| Number num -> String.replicate num “timey wimey”
| Name str -> sprintf “%s is my favorite episode” desc

17. let wibblyWobbly episode =
match episode.Identifier with
| Number num -> String.replicate num “timey wimey”

18. let wibblyWobbly episode =
match episode.Identifier with
| Number num -> String.replicate num “timey wimey”

19. So why are Algebraic Data Types so cool?
➢ The flexibility and expressiveness of
dynamic type systems
➢ The security and support of static types
systems

20. “DOMAIN MODELING MADE FUNCTIONAL!!!
AND F# FOR FUN AND PROFIT!!!
BY SCOTT WLASCHIN!!!”

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