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Phase Next

These are much less well considered! The primary reason for documenting them now is merely to make sure that nothing in Phase One blocks future development.

Condition System

  • adopt matchure as general purpose matching strategy
    • update implementation to use protocols instead of multimethods
    • matching will work with class of plain Java exceptions
    • and also work with maplikeness of Clojure exceptions
  • How to prevent people from writing handlers that rely on debug-build information?
    • yes: warn users through documentation
    • no: parse matching forms and reject
    • no: give locals and bindings ugly "debug" names
  • possible approach
    • extend try/catch/finally with handle
    • handle takes two args: error and context
    • match on error to grab exceptions unwinding
    • then walk stack of registered handlers, matching on context
      • note that context is arbitrary object
      • it could be, or include, the error!
    • handler is fn of two args (error, context)
      • if not a fn, could be literal value for simple case
    • tools would be able to allow interactive restart, a la CL
    • note that this approach puts more responsibility on top and less on middle (when compared to CL)

Better Java Unification

  • ISnapshot protocol identifies Java objects that can be "immutable data-ized"
    • protocol extends to throwable
    • other possible cool uses
      • dynamic codegen of nonreflective code a la clojure.core/bean
  • extend condition system to call through ISnapshot where available
    • get power of matching with plain ol' Java exceptions!
  • simplify REPL and reporting code
    • all exceptions can now be treated as data, from Java or from Clojure
  • would snaphsot need to be memoized ??
    • probably
    • simple LRU might be good enough
    • or could use a weak map keyed by base object
      • do exceptions consume any native resources?
  • if unification with Java was good enough, could we drop the Clojure-specific exceptions?
    • unlikely – bottom needs to be separable
    • if IMeta or IPersistentMap were protocols...
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