notes

Evaluator
  * globalActivation : Activation
  * currentActivation : Activation
  + step() : Boolean
  + run() : Void

Activation
  * args : Array<Object>
  * vars : Map<String, Object>
  * parent : Activation
  * caller : Activation
  * stack : Array<Object>
  * nextInstruction : Instruction
  + methodActivation : MethodActivation
  + step() : Activation
  + iPush(value : Object) : Activation
  + iDrop() : Activation
  + iNonLocalReturn(value : Object) : Activation
  + iReturn(value : Object) : Activation
  + declVar(name : String, value : Object) : Void
  + setVar(name : String, value : Object) : Void
  + getVar(name : String) : Object
  + getDeclActivation(name : String) : Activation
  + hasVar(name : String) : Boolean
  + classOf(obj : Object) : Class

MethodActivation <: Activation
  * method : Method
  * receiver : Object

BlockActivation <: Activation
  * block : Block
  + return(value : Object) : Activation

Method
  * formals : Array<String>
  * code : Instruction

Block <: Object
  * formals : Array<String>
  * code : Instruction
  * parent : Activation

Instruction
  + eval(a: Activation) : Activation
  // just call the equivalent method in Activation

PushValue <: Instruction
  * next : Instruction
  * value : Object

PushVar <: Instruction
  * next : Instruction
  * name : String

PopIntoVar <: Instruction
  * next : Instruction
  * name : String

DeclVar <: Instruction
  * next : Instruction
  * name : String

Drop <: Instruction
  * next : Instruction

Call <: Instruction
  * next : Instruction
  * selector : String
  * numArgs : Number

ReturnFromBlock <: Instruction
  * next : Instruction

Cond <: Instruction
  * nextIfTrue : Instruction
  * nextIfFalse : Instruction

-------------------------

Class
  * superClass : Class
  * methods : Map<String, Method>
  * instVarNames : Set<String>
  + newInstance() : Instance<Class>
  + lookup(selector : String) : Method

PushThis <: Instruction
  * next : Instruction

PushInstVar <: Instruction
  * next : Instruction
  * name : String

PopIntoInstVar <: Instruction
  * next : Instruction
  * name : String

MakeNew <: Instruction
  * next : Instruction

ReturnFromMethod <: Instruction
  * next : Instruction