Conservative Language Use For Fun and Profit

Scala provides many tools for building programs. Depending on how you
look at it, this can be a great thing, or a terrifying thing. I will
take a look at the scala "sub-set" that I adopted over years of pain,
and hopefully demonstrate that you can get more benefit from scala by
adopting less of it. In the end my sub-set may be different to yours,
but it might give you some different ideas on how to approach
programming in scala (or in general).

Transcript

1. Conservative Mark Hibberd Scala
2. You can make better use of tools by having deep knowledge of a tool, but only applying a specialised subset of its features. Claim #1
3. You can’t effectively control your use of tools to a specialised subset unless you have very deep knowledge of the tool. Claim #2
4. Programming languages are just tools. Claim #3
5. Conservative usage patterns generalise to lots of tools not just languages. Claim #4
7. SCALA a primer
8. 1 scala> val x = List("1", "2", "3", "4").toSet() + "5" 2 3 scala> println(x) 4 5 output: 6 7 ???
9. 1 scala> val x = List("1", "2", "3", "4").toSet() + "5" 2 3 scala> println(x) 4 5 output: 6 7 false5
10. 1 scala> println({} + "") 2 3 output: 4 5 ???
11. 1 scala> println({} + "") 2 3 output: 4 5 ()
12. 1 scala> val x = Option(1).zip(Option(1)) == 2 Option((1, 1)) 3 4 scala> println(x) 5 6 output: 7 8 ???
13. 1 scala> val x = Option(1).zip(Option(1)) == 2 Option((1, 1)) 3 4 scala> println(x) 5 6 output: 7 8 false
14. 1 scala> val x = Option(1).zip(Option(1)) == 2 List((1, 1)) 3 4 scala> println(x) 5 6 output: 7 8 ???
15. 1 scala> val x = Option(1).zip(Option(1)) == 2 List((1, 1)) 3 4 scala> println(x) 5 6 output: 7 8 true
16. 1 scala> val x = Option(1).zip(Option(1)) == 2 Vector((1, 1)) 3 4 scala> println(x) 5 6 output: 7 8 true
18. scalac thinks your code is bad
19. 1 List("1", "2", "3", "4").toSet() + “5"
20. 1 List("1", "2", "3", "4").toSet() + "5" 2 3 // example.scala:1: error: not enough arguments for 4 // method apply: (elem: Any)Boolean in trait GenSet. 5 // Unspecified value parameter elem. -Yno-adapted-args
21. 1 def update(data: String): Future[Unit] = for { 2 n <- get 3 _ <- save(n, data) 4 } yield set(n + 1) 5 6 def get: Future[Int] = 7 ??? 8 9 def set(n: Int): Future[Int] = 10 ??? 11 12 def save(n: Int, data: String): Future[Unit] = 13 ???
22. 1 def update(data: String): Future[Unit] = for { 2 n <- get 3 _ <- save(n, data) 4 } yield set(n + 1) 5 6 //example.scala:4: warning: discarded non-Unit value -Ywarn-value-discard
23. -Xlint / -Ywarn-all https://github.com/scala/scala/blob/v2.10.3/src/compiler/scala/tools/nsc/settings/ Warnings.scala#L18-L44
24. -Xfatal-warnings
25. -Yno-predef
26. scala scala vs
27. Lets reduce the surface area of the language we have to worry about
28. Lets not save characters by risking correctness
29. Lets not make it “easy” by building APIs using ever scala feature ever
30. Lets do more with less
31. Syntax
32. Types & Inference
33. Closed better than Open
34. Don’t confuse Types and Data
35. Scala does not have Type Inference
36. Variance or Not
37. Any is the same as not having Types
38. Implicits
39. Type Classes vs Global Mutable HashMaps
40. Syntactic Extensions
41. Scala is just a Tool
42. Performance vs Correctness
43. Concurrent Scala is not a Win
44. Integration not Ecosystem
45. End Game