This presentation shows how to use "fold algebras" to implement a toy DSL for paths

1. Writing a DSL with
a Fold-Algebra
ScalaSyd

2. Overview
The expression problem
Fold-algebras
File paths
DSLs tips and tricks
Scala types

3. I’ve had this problem
Result
Failure Success Pending
Console Html
Screenshot?
Pdf?

4. The Expression Problem
Add(Lit(1), Lit(2))

5. The Expression Problem

6. The Expression Problem

7. Solved in Java?!?

8. Data as an ADT

9. List as a “fold”

10. List as a “fold”

11. Data types encodings
List[A] = Nil + (A, List[A])
F[A] -> A
Nil + (A, List[A]) -> A
(Nil -> A, (A, List[A]) -> A)

12. A Fold-algebra for directories
Name Name Name Name

13. A Fold-algebra for directories

14. A DSL for directories

15. What’s in a name?

16. What’s in a name?

17. A DSL for directories

18. A DSL for directories

19. A DSL for directories

20. A Fold-algebra for files

21. A DSL for files

22. A DSL for files

23. A Fold-algebra for paths

24. A Fold-algebra for paths

25. A DSL for relative paths

26. A DSL for relative paths

27. A DSL for relative paths

28. A DSL for relative paths

29. A DSL for relative paths

30. A DSL for relative paths

31. Conclusion
Papers! Play!
Present at
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3Ps