Declarative programming winning examples

Lightning talk for PyWeb #40

Transcript

1. Declarative Programming winning examples Udi h Bauman, CloudLock
2. Declarative Programming winning examples Udi h Bauman, CloudLock We’re hiring, check us out!
3. Declarative Programming is a form of high-level programming:
4. Declarative Programming is a form of high-level programming: telling your software what to do, instead of how to do it
5. Some real-life patterns 1. “what”-metadata driven 2. high-level “what”-code 3. “how”-code abstracted away
6. 1. “what”-metadata driven • problem: you have many behaviours that only differ in parameters or small variants of behaviour
7. 1. “what”-metadata driven • problem: you have many behaviours that only differ in parameters or small variants of behaviour • solution: write metadata & code that derives behaviour from metadata
8. 1. “what”-metadata driven • problem: you have many behaviours that only differ in parameters or small variants of behaviour • solution: write metadata & code that derives behaviour from metadata • benefit: adding new behaviours now means just adding metadata, & in rare cases also overriding classes/functions
9. Example: rollups aggregation
10. Example: rollups aggregation
11. 2. high-level “what”-code • problem: you have many behaviours that only differ in the “edges”
12. 2. high-level “what”-code • problem: you have many behaviours that only differ in the “edges” • old solution: using inheritance tricks such as template method &c
13. 2. high-level “what”-code • problem: you have many behaviours that only differ in the “edges” • newer solution: abstract the algorithm to declarative high-level code & “chain” the overriding behaviour
14. 2. high-level “what”-code • problem: you have many behaviours that only differ in the “edges” • newer solution: abstract the algorithm to declarative high-level code & “chain” the overriding behaviour • benefit: see the big picture & just the relevant details
15. Example: d3: data-driven documents
16. Example: d3: data-driven documents
17. 3. “how”-code abstracted away • problem: if some code addresses requirements that are obvious & not specific to your app, why should it be there?
18. 3. “how”-code abstracted away • problem: if some code addresses requirements that are obvious & not specific to your app, why should it be there? • solution: abstract that code in an underlying framework, either yours or someone’s else
19. 3. “how”-code abstracted away • problem: if some code addresses requirements that are obvious & not specific to your app, why should it be there? • solution: abstract that code in an underlying framework, either yours or someone’s else • benefit: simple, small code just for the requirements specific to your app
20. Example 1: <your favorite framework>
21. Example 2: Meteor • if a user is looking at a list of records, obviously when a new record is added, the user should see it • & if he changes a record, obviously other users looking at it should see the modification • so why should you implement this?
22. Example 2: Meteor • So what's declarative here? ◦ You are left with just declarations: ▪ What data the server publishes ▪ What data the client subscribes to ▪ What data is shown in the UI • See this list of 8 open-source apps written in Meteor: http://meteorapps.co ◦ Except for one they are all well written & worth learning from..
23. Thanks for listening. @dibau_naum_h