dsls with fold algebras
DESCRIPTION
This presentation shows how to use "fold algebras" to implement a toy DSL for pathsTRANSCRIPT
Writing a DSL with a Fold-Algebra
ScalaSyd
Overview
Fold-algebras
File paths
DSLs tips and tricks
The expression problem
Scala types
I’ve had this problem
Result
Failure Success Pending
Console Html
Screenshot?
Pdf?
The Expression Problem
Add(Lit(1), Lit(2))
The Expression Problem
The Expression Problem
Solved in Java?!?
Data as an ADT
List as a “fold”
List as a “fold”
foldRight
or foldLeft?
then map, filter,
flatMap,…
Data types encodings
Fold-
Algebra
(Nil -> A, (A, List[A]) -> A)
F-Algebra
Nil + (A, List[A]) -> A F[A] -> A
List[A] = Nil + (A, List[A])
A Fold-algebra for directories
Name Name Name Name
A Fold-algebra for directories
return an object
doing what you
want!
A DSL for directories
Create
directorie
s?
What’s in a name?
this is
obviously
correct
What’s in a name?
With
macros!
A DSL for directories
Derived
methods
A DSL for directories
Implicit
class
A DSL for directories
What about files?
A Fold-algebra for files
Extend!
A DSL for files
A DSL for files
What about absolute,
relative paths?
A Fold-algebra for paths
Poor Man’s e
num
A Fold-algebra for paths
Type member
A DSL for relative paths
Singleton
type
A DSL for relative paths
A DSL for relative paths
Type alias
“Conform”
type
A DSL for relative paths
Path-dependent
type
A DSL for relative paths
Path-dependent
type
A DSL for relative paths
Conclusion
Play!Papers!
Present at !
Ps3