What the JVM needs

Notes from Rich Hickey's workshop

user mode limitations

• please optimize this
• fences
• typestate: now immutable - especially arrays (typically encapsulated in non-writing header, a la java.lang.String)
• Why Tailcalls: as a guarantee, not just an optimization

numbers

• fixnums
• need a uniform entry/exit types (Object => boxing)
• Hacker's delight overflow detection is OK (only for add/sub); need a static method that throws overflow-exception?

storage management

• floating garbage foo(o, o=null); is tailcall a solution?

limits

• 31-bit arrays
• 16-bit instructions
• static data structures (array literals)

types

• structs (efficient pointerless element selection)
• value types (no mutability, acmp-identity, id-hashcode, monitorenter)
• immutable arrays = array-like value types