Event Type Polymorphism

Transcription

1 Event Type Polymorphism Rex D. Fernando Robert Dyer Hridesh Rajan Department of Computer Science Iowa State University This work was supported in part by NSF grant CCF

2 : Code re-use and specialization for event-based separation of concerns Approach: Event Type Polymorphism in Ptolemy Technical Contributions: Formal semantics for event type polymorphism Simpler semantics, when compared to earlier work Rex D. Fernando, Robert Dyer and Hridesh Rajan 1 Event Type Polymorphism

3 An Example - No Event Type Polymorphism Example Revisited - With Event Type Polymorphism AST MultExp DivExp NumExp NumExp NumExp Rex D. Fernando, Robert Dyer and Hridesh Rajan 2 Event Type Polymorphism

4 An Example - No Event Type Polymorphism Example Revisited - With Event Type Polymorphism AST MultExp Events MultVisited DivExp NumExp NumExp NumExp C E class C announces event E Rex D. Fernando, Robert Dyer and Hridesh Rajan 2 Event Type Polymorphism

5 An Example - No Event Type Polymorphism Example Revisited - With Event Type Polymorphism AST MultExp Events MultVisited DivExp NumExp DivVisited NumExp NumExp C E class C announces event E Rex D. Fernando, Robert Dyer and Hridesh Rajan 2 Event Type Polymorphism

6 An Example - No Event Type Polymorphism Example Revisited - With Event Type Polymorphism AST MultExp Events MultVisited DivExp NumExp DivVisited NumExp NumExp NumVisited C E class C announces event E Rex D. Fernando, Robert Dyer and Hridesh Rajan 2 Event Type Polymorphism

7 An Example - No Event Type Polymorphism Example Revisited - With Event Type Polymorphism AST MultExp Events MultVisited Handlers Tracing DivExp NumExp DivVisited TypeCheck NumExp NumExp NumVisited Evaluation C E class C announces event E E H event E's announcement invokes handler H Rex D. Fernando, Robert Dyer and Hridesh Rajan 2 Event Type Polymorphism

8 An Example - No Event Type Polymorphism Example Revisited - With Event Type Polymorphism AST MultExp Events MultVisited Handlers Tracing DivExp NumExp DivVisited TypeCheck NumExp NumExp NumVisited Evaluation C E class C announces event E E H event E's announcement invokes handler H Rex D. Fernando, Robert Dyer and Hridesh Rajan 2 Event Type Polymorphism

9 An Example - No Event Type Polymorphism Example Revisited - With Event Type Polymorphism AST Events Handlers MultExp MultVisited Tracing DivExp NumExp DivVisited TypeCheck NumExp NumExp NumVisited Evaluation C E class C announces event E E H event E's announcement invokes handler H Rex D. Fernando, Robert Dyer and Hridesh Rajan 2 Event Type Polymorphism

10 An Example - No Event Type Polymorphism Example Revisited - With Event Type Polymorphism MultVisited + node : MultExp + left : Exp + right : Exp DivVisited + node : DivExp + left : Exp + right : Exp PlusVisited + node : PlusExp + left : Exp + right : Exp Rex D. Fernando, Robert Dyer and Hridesh Rajan 3 Event Type Polymorphism

11 An Example - No Event Type Polymorphism Example Revisited - With Event Type Polymorphism MultVisited + node : MultExp + left : Exp + right : Exp DivVisited + node : DivExp + left : Exp + right : Exp PlusVisited + node : PlusExp + left : Exp + right : Exp Rex D. Fernando, Robert Dyer and Hridesh Rajan 3 Event Type Polymorphism

12 An Example - No Event Type Polymorphism Example Revisited - With Event Type Polymorphism MultVisited + node : MultExp + left : Exp + right : Exp DivVisited + node : DivExp + left : Exp + right : Exp PlusVisited + node : PlusExp + left : Exp + right : Exp Rex D. Fernando, Robert Dyer and Hridesh Rajan 3 Event Type Polymorphism

13 An Example - No Event Type Polymorphism Example Revisited - With Event Type Polymorphism class ASTTracer { void printmult ( MultVisited next ) { logvisitbegin ( next. node (). getclass ()); next. invoke (); logvisitend ( next. node (). getclass ()); } when MultVisited do printmult ; void printdiv ( DivVisited next ) { logvisitbegin ( next. node (). getclass ()); next. invoke (); logvisitend ( next. node (). getclass ()); } when DivVisited do printdiv ; } void printplus ( PlusVisited next ) { logvisitbegin ( next. node (). getclass ()); next. invoke (); logvisitend ( next. node (). getclass ()); } when PlusVisited do printplus ; Rex D. Fernando, Robert Dyer and Hridesh Rajan 4 Event Type Polymorphism

14 An Example - No Event Type Polymorphism Example Revisited - With Event Type Polymorphism class ASTTracer { void printmult ( MultVisited next ) { logvisitbegin ( next. node (). getclass ()); next. invoke (); logvisitend ( next. node (). getclass ()); } when MultVisited do printmult ; void printdiv ( DivVisited next ) { logvisitbegin ( next. node (). getclass ()); next. invoke (); logvisitend ( next. node (). getclass ()); } when DivVisited do printdiv ; } void printplus ( PlusVisited next ) { logvisitbegin ( next. node (). getclass ()); next. invoke (); logvisitend ( next. node (). getclass ()); } when PlusVisited do printplus ; Rex D. Fernando, Robert Dyer and Hridesh Rajan 5 Event Type Polymorphism

15 An Example - No Event Type Polymorphism Example Revisited - With Event Type Polymorphism Can we re-use code here? What happens if a new AST type is added? What happens if an AST type is removed? Rex D. Fernando, Robert Dyer and Hridesh Rajan 6 Event Type Polymorphism

16 An Example - No Event Type Polymorphism Example Revisited - With Event Type Polymorphism Can we re-use code here? No! Passing event closures (next) as argument is illegal. (to simplify reasoning about invoke/proceed functionality) What happens if a new AST type is added? What happens if an AST type is removed? Rex D. Fernando, Robert Dyer and Hridesh Rajan 6 Event Type Polymorphism

17 An Example - No Event Type Polymorphism Example Revisited - With Event Type Polymorphism Can we re-use code here? No! Passing event closures (next) as argument is illegal. (to simplify reasoning about invoke/proceed functionality) What happens if a new AST type is added? Must update all handlers to support that node type! What happens if an AST type is removed? Rex D. Fernando, Robert Dyer and Hridesh Rajan 6 Event Type Polymorphism

18 An Example - No Event Type Polymorphism Example Revisited - With Event Type Polymorphism Can we re-use code here? No! Passing event closures (next) as argument is illegal. (to simplify reasoning about invoke/proceed functionality) What happens if a new AST type is added? Must update all handlers to support that node type! What happens if an AST type is removed? Must update all handlers and remove that node type! Rex D. Fernando, Robert Dyer and Hridesh Rajan 6 Event Type Polymorphism

19 An Example - No Event Type Polymorphism Example Revisited - With Event Type Polymorphism Can we re-use code here? No! Passing event closures (next) as argument is illegal. (to simplify reasoning about invoke/proceed functionality) What happens if a new AST type is added? Must update all handlers to support that node type! What happens if an AST type is removed? Must update all handlers and remove that node type! Polymorphism can help us here! Rex D. Fernando, Robert Dyer and Hridesh Rajan 6 Event Type Polymorphism

20 An Example - No Event Type Polymorphism Example Revisited - With Event Type Polymorphism ExpVisited + node : Exp BinArithVisited + node : BinArith + left : Exp + right : Exp MultVisited + node : MultExp DivVisited + node : DivExp PlusVisited + node : PlusExp Rex D. Fernando, Robert Dyer and Hridesh Rajan 7 Event Type Polymorphism

21 An Example - No Event Type Polymorphism Example Revisited - With Event Type Polymorphism ExpVisited + node : Exp BinArithVisited + node : BinArith + left : Exp + right : Exp MultVisited + node : MultExp DivVisited + node : DivExp PlusVisited + node : PlusExp Rex D. Fernando, Robert Dyer and Hridesh Rajan 7 Event Type Polymorphism

22 An Example - No Event Type Polymorphism Example Revisited - With Event Type Polymorphism ExpVisited + node : Exp BinArithVisited + node : BinArith + left : Exp + right : Exp MultVisited + node : MultExp DivVisited + node : DivExp PlusVisited + node : PlusExp Rex D. Fernando, Robert Dyer and Hridesh Rajan 7 Event Type Polymorphism

23 An Example - No Event Type Polymorphism Example Revisited - With Event Type Polymorphism class ASTTracer { void printexp ( ExpVisited next ) { logvisitbegin ( next. node (). getclass ()); next. invoke (); logvisitend ( next. node (). getclass ()); } when ExpVisited do printexp ; } Rex D. Fernando, Robert Dyer and Hridesh Rajan 8 Event Type Polymorphism

24 An Example - No Event Type Polymorphism Example Revisited - With Event Type Polymorphism class ASTTracer { void printexp ( ExpVisited next ) { logvisitbegin ( next. node (). getclass ()); next. invoke (); logvisitend ( next. node (). getclass ()); } when ExpVisited do printexp ; } Quantifying over entire event hierarchy by only naming super event! No need to update when a new AST type added! No need to update when an AST type removed! Rex D. Fernando, Robert Dyer and Hridesh Rajan 8 Event Type Polymorphism

25 An Example - No Event Type Polymorphism Example Revisited - With Event Type Polymorphism class ASTTracer { void printexp ( ExpVisited next ) { logvisitbegin ( next. node (). getclass ()); next. invoke (); logvisitend ( next. node (). getclass ()); } when ExpVisited do printexp ; } Quantifying over entire event hierarchy by only naming super event! No need to update when a new AST type added! No need to update when an AST type removed! Let s take a look at the language... Rex D. Fernando, Robert Dyer and Hridesh Rajan 8 Event Type Polymorphism

26 Syntax Type-checking Rules Sub-event Relation decl ::= class c extends d { field* meth* binding* } c event p extends q { form* } where c C, a set of class names d C {Object}, a set of superclass names p P, a set of event type names q P {Event}, a set of super event type names Rex D. Fernando, Robert Dyer and Hridesh Rajan 9 Event Type Polymorphism

27 Syntax Type-checking Rules Sub-event Relation binding ::= when p do m e ::= register(e) unregister(e) announce p (e*) { e } e.invoke() where m M, a set of method names Rex D. Fernando, Robert Dyer and Hridesh Rajan 10 Event Type Polymorphism

28 Syntax Type-checking Rules Sub-event Relation (check event) isclass(c) i [1..n] :: isclass(t i ) p : q Π c event p extends q {t 1 var 1,..., t n var n } : OK Rex D. Fernando, Robert Dyer and Hridesh Rajan 11 Event Type Polymorphism

29 Syntax Type-checking Rules Sub-event Relation ( : Top) isevent(p) p : Event ( : Reflexive) isevent(p) p : p ( : Transitive) isevent(p) isevent(q) isevent(q ) p : q q : q p : q Rex D. Fernando, Robert Dyer and Hridesh Rajan 12 Event Type Polymorphism

30 Syntax Type-checking Rules Sub-event Relation ( : Base) (c event p extends q {t 1 var 1,..., t n var n }) CT isevent(q) [t 1 var 1,..., t m var m] = contextsof (q) i [1..n] :: t i var i [t 1 var 1,..., t n var n ] ( j [1..m] :: t j var i [t 1 var 1,..., t m var m] t i <: t j) p : q contextsof recursively computes the list of all context for an event type q, based on its supertypes Rex D. Fernando, Robert Dyer and Hridesh Rajan 13 Event Type Polymorphism

31 Syntax Type-checking Rules Sub-event Relation New syntax: p extends q Typing rules use new relation: p : q Both depth and width subtyping of context information Rex D. Fernando, Robert Dyer and Hridesh Rajan 14 Event Type Polymorphism

32 Related Work Overview Implicit Invocation + Implicit Announcement [Steimann 2010] Implicit announcement allows ambiguity Harder to reason about what event(s) announced Escala [Gasiunas 2011] Does not support width subtyping Limits the ability to specialize sub-events Rex D. Fernando, Robert Dyer and Hridesh Rajan 15 Event Type Polymorphism

33 Future Work Overview Finish type-soundness proof (in Coq) Implement semantics in OpenJDK-based Ptolemy compiler Non-trivial to implement Rex D. Fernando, Robert Dyer and Hridesh Rajan 16 Event Type Polymorphism

34 : Code re-use and specialization for event-based separation of concerns Ability to quantify over a hierarchy of events Allows for code re-use in event definitions and handlers Better maintenance - for both adding and removing events Approach: Event Type Polymorphism in Ptolemy Event types have inheritance Allow width and depth subtyping of context Handlers also handle sub-events Technical Contributions: Formal semantics for event type polymorphism Simpler semantics, when compared to earlier work Rex D. Fernando, Robert Dyer and Hridesh Rajan 17 Event Type Polymorphism

35 Questions?

36

37 Appendix Full Syntax Auxilliary Methods Type-checking Rules Future Work prog ::= decl* e decl ::= class c extends d { field* meth* binding* } c event p extends q { form* } where c C, a set of class names d C {Object}, a set of superclass names p P, a set of event type names q P {Event}, a set of super event type names Rex D. Fernando, Robert Dyer and Hridesh Rajan 18 Event Type Polymorphism

38 Appendix Full Syntax Auxilliary Methods Type-checking Rules Future Work t ::= c thunk p field ::= c f meth ::= c m (form*) { e } form ::= t var, where var this binding ::= when p do m where f F, a set of field names m M, a set of method names var {this} V, V is a set of variable names Rex D. Fernando, Robert Dyer and Hridesh Rajan 19 Event Type Polymorphism

39 Appendix Full Syntax Auxilliary Methods Type-checking Rules Future Work ep ::= n var ep.f ep!= null ep == ep ep < ep! ep ep && ep e ::= new c() var null e.m(e*) e.f e.f = e cast c e form = e ; e e ; e if (ep) { e } else { e } while (ep) { e } register(e) unregister(e) announce p (e*) { e } e.invoke() where n Z, the set of integers Rex D. Fernando, Robert Dyer and Hridesh Rajan 20 Event Type Polymorphism

40 Appendix Full Syntax Auxilliary Methods Type-checking Rules Future Work (Concrete Type Inh.) var i {var 1,..., var n } concretetype(t i var i, [t 1 var 1,..., t n var n ]) = t i var i (Concrete Type Depth) j [1..n] :: t j var i [t 1 var 1,..., t n var n ] concretetype(t i var i, [t 1 var 1,..., t n var n ]) = t j var i Rex D. Fernando, Robert Dyer and Hridesh Rajan 21 Event Type Polymorphism

41 Appendix Full Syntax Auxilliary Methods Type-checking Rules Future Work (Top Context Vars) contextsof (Event) = (Context Vars) (c event p extends q {t 1 var 1,..., t n var n }) CT [t 1 var 1,..., t m var m] = contextsof (q) contextsof (p) = [ i [1..m] :: concretetype(t i var i, [t 1 var 1,..., t n var n ])] + [ i [1..n] :: t i var i :: var i {var 1,..., var m})] Rex D. Fernando, Robert Dyer and Hridesh Rajan 22 Event Type Polymorphism

42 Appendix Full Syntax Auxilliary Methods Type-checking Rules Future Work ExpVisited + node : Exp BinArithVisited + node : BinArith + left : Exp + right : Exp contextsof(expvisited) = [node:exp] contextsof(binarithvisited) = [node:binarith, left:exp, right:exp] contextsof(divvisited) = [node:divexp, left:exp, right:exp] DivVisited + node : DivExp Rex D. Fernando, Robert Dyer and Hridesh Rajan 23 Event Type Polymorphism

43 Appendix Full Syntax Auxilliary Methods Type-checking Rules Future Work (Is Event) (c event p extends q {t 1 var 1,..., t n var n }) CT isevent(p) Rex D. Fernando, Robert Dyer and Hridesh Rajan 24 Event Type Polymorphism

44 Appendix Full Syntax Auxilliary Methods Type-checking Rules Future Work ( : Top) isevent(p) p : Event ( : Refl.) isevent(p) p : p ( : Trans.) isevent(p) isevent(q) isevent(q ) p : q q : q p : q Rex D. Fernando, Robert Dyer and Hridesh Rajan 25 Event Type Polymorphism

45 Appendix Full Syntax Auxilliary Methods Type-checking Rules Future Work ( : Base) (c event p extends q {t 1 var 1,..., t n var n }) CT isevent(q) [t 1 var 1,..., t m var m] = contextsof (q) i [1..n] :: t i var i [t 1 var 1,..., t n var n ] ( j [1..m] :: t j var i [t 1 var 1,..., t m var m] t i <: t j) p : q Rex D. Fernando, Robert Dyer and Hridesh Rajan 26 Event Type Polymorphism

46 Appendix Full Syntax Auxilliary Methods Type-checking Rules Future Work θ ::= type attributes OK program/top-level declaration OK in c method, binding var t var/formal/field exp t expression τ ::= c class type expressions π, Π ::= {I : θ I } I K, type environments where K is finite, K (L {this} V) Rex D. Fernando, Robert Dyer and Hridesh Rajan 27 Event Type Polymorphism

47 Appendix Full Syntax Auxilliary Methods Type-checking Rules Future Work (check event) isclass(c) i [1..n] :: isclass(t i ) p : q Π c event p extends q {t 1 var 1,..., t n var n } : OK Rex D. Fernando, Robert Dyer and Hridesh Rajan 28 Event Type Polymorphism

48 Appendix Full Syntax Auxilliary Methods Type-checking Rules Future Work (check binding) isclass(c ) (c event p extends q {t 1 var 1,..., t n var n }) CT c <: c (c m(thunk p var){e}) = methodbody(c, m) Π when p do m : OK in c Rex D. Fernando, Robert Dyer and Hridesh Rajan 29 Event Type Polymorphism

49 Appendix Full Syntax Auxilliary Methods Type-checking Rules Future Work (announce exp type) (c event p extends q {t 1 var 1,..., t n var n }) CT i [1..n] :: Π e i : exp t i Π e : exp c c <: c Π announce p(e 1,..., e n ) {e} : exp c Rex D. Fernando, Robert Dyer and Hridesh Rajan 30 Event Type Polymorphism

50 Implementation Appendix Full Syntax Auxilliary Methods Type-checking Rules Future Work Static semantics are relatively simple But implementation is non-trivial Handling a supertype event requires the entire hierarchy rooted by that event also be registered But to maintain separate compilation and type checking, event types are only aware of their direct supertype What happens when loading new subtypes and handlers already registered? Rex D. Fernando, Robert Dyer and Hridesh Rajan 31 Event Type Polymorphism