Virtual MeetUp Tuesday April 7
Time: 10:00 AM Pacific / 5:00 PM GMT
Location: Lucy's dedicated Google Hangout: http://s.apache.org/lucy-hangout.
To participate, log into Google Plus, then join the videochat.
If you're having difficulty joining the Hangout, find us at the #lucy_dev IRC channel on irc.freenode.net.
- Introductions (10 minutes)
- Interfaces (30 minutes)
- Open discussion / more about interfaces (20 minutes)
This MeetUp will take the form of a Lucy Book Club discussion: participants will answer questions prepared by other participants on the theme. Feel free to bring your own questions!
General discussion questions for interfaces:
- It is impossible to add a method a Go interface without breaking backwards compatibility. Same with Java interfaces prior to Java 8. Why?
- Why is it possible to add methods to an abstract class without breaking backwards compatibility?
- What is a "default method" in Java 8? How do default methods make it possible to modify a Java interface without breaking backwards compatibility?
- How might you emulate abstract methods in a dynamic programming language?
- How might you emulate interfaces (without default methods) in a dynamic programming language?
- How might you emulate interfaces (with default methods) in a dynamic programming language?
- What's the difference between a "mixin" and an interface consisting entirely of default methods (i.e. with no abstract methods)?
Clownfish/Lucy-specific discussion questions for interfaces:
Should Lucy's Query class be an interface instead of an abstract class? How about Analyzer, Searcher, Matcher, Collector, Compiler, IndexReader, DataReader, DataWriter, Lexicon, Posting, Folder, FileHandle, Lock, and SortExternal -- all of which are abstract classes?
There are a handful of Lucy classes which are designed to be subclassed by users but are not abstract: QueryParser, IndexManager, Schema, FieldType, and Highlighter. Why is it challenging to change these to interfaces?
- How can we change the Clownfish callback mechanism to be based on interfaces instead of classes?
- Should Obj#Hash_Sum be moved to a "Hasher" interface? Should Obj#Clone be moved to a "Cloner" interface? Should Obj have any methods at all?
- What are covariant return types?
- Why is duck typing easier using hashtable-based method dispatch than vtable-based method dispatch?
Optional reading materials: