Add `scanl` and `scanr`

[runarorama]

This adds scanr and scanl for List, and the corresponding functions for Nonempty. Includes pretty good tests and lots of examples.

Also added:

• Boolean.and and Boolean.or as first-class functions.

• Doc.example for constructing an example from a termRef.

  The changes summarized below are available for you to review, using the following command:

  pull-request.load https://github.com/unisonweb/base:.trunk https://github.com/runarorama/mybase:._topic.scan

  Added definitions:

  1. Boolean.and : Boolean -> Boolean -> Boolean (+3 metadata)
  2. Boolean.and.doc : Doc (+2 metadata)
  3. Boolean.or : Boolean -> Boolean -> Boolean (+3 metadata)
  4. Boolean.or.doc : Doc (+2 metadata)
  5. Doc.example : Term -> Doc (+3 metadata)
  6. Doc.example.doc : Doc (+2 metadata)
  7. List.Nonempty.scanl : (a ->{e} a ->{e} a) -> Nonempty a ->{e} Nonempty a (+3 metadata)
  8. List.Nonempty.scanl.doc : Doc (+2 metadata)
  9. List.Nonempty.scanl.examples.asDoc : Doc (+2 metadata)
  10. List.Nonempty.scanl.test : [Test.Result] (+3 metadata)
  11. List.Nonempty.scanr : (a ->{e} a ->{e} a) -> Nonempty a ->{e} Nonempty a (+3 metadata)
  12. List.Nonempty.scanr.doc : Doc (+2 metadata)
  13. List.Nonempty.scanr.examples.asDoc : Doc (+2 metadata)
  14. List.Nonempty.scanr.test : [Test.Result] (+3 metadata)
  15. List.scanl : (b ->{e} a ->{e} b) -> b -> [a] ->{e} Nonempty b (+3 metadata)
  16. List.scanl.doc : Doc (+2 metadata)
  17. List.scanl.examples.asDoc : Doc (+2 metadata)
  18. List.scanl.examples.ex1 : Nonempty Nat (+2 metadata)
  19. List.scanl.examples.ex2 : Nonempty Nat (+2 metadata)
  20. List.scanl.examples.ex3 : Nonempty Nat (+2 metadata)
  21. List.scanl.examples.ex4 : Nonempty Nat (+2 metadata)
  22. List.scanl.examples.ex5 : Nonempty Nat (+2 metadata)
  23. List.scanl.test : [Test.Result] (+3 metadata)
  24. List.scanr : (a ->{e} b ->{e} b) -> b -> [a] ->{e} Nonempty b (+3 metadata)
  25. List.scanr.doc : Doc (+2 metadata)
  26. List.scanr.examples.asDoc : Doc (+2 metadata)
  27. List.scanr.examples.ex1 : Nonempty Nat (+2 metadata)
  28. List.scanr.examples.ex2 : Nonempty Nat (+2 metadata)
  29. List.scanr.examples.ex3 : Nonempty Nat (+2 metadata)
  30. List.scanr.examples.ex4 : Nonempty Boolean (+2 metadata)
  31. List.scanr.examples.ex5 : Nonempty Nat (+2 metadata)
  32. List.scanr.test : [Test.Result] (+3 metadata)

[runarorama]

Merged in base hash #4un3bevvfc.