Changing to new object model of core-lib

Introduction of AbstractObject without fields and classes.
Methods are not Arrays anymore to simplify and avoid use of 'object fields'.
Frames are not entirely implementation specific.

- clean out superficial comments
- added missing primitives
Signed-off-by: Stefan Marr <git@stefan-marr.de>

core-lib @ b2d362a1

-Subproject commit 555c692765b3853feb7fa3cdcd260440d9ec1422
+Subproject commit b2d362a1f4ffdb6a2a6ad036eb8d582073ddad45

src/som/compiler/class_generation_context.py

@@ -67,7 +67,7 @@ class ClassGenerationContext(object):
         result_class.set_instance_invokables(self._universe.new_array_from_list(self._class_methods))
         result_class.set_name(self._universe.symbol_for(ccname))
 
-        super_mclass = super_class.get_class()
+        super_mclass = super_class.get_class(self._universe)
         result_class.set_super_class(super_mclass)
 
         # Allocate the resulting class
@@ -86,6 +86,6 @@ class ClassGenerationContext(object):
         system_class.set_instance_fields(self._universe.new_array_from_list(self._instance_fields))
     
         # class-bound == class-instance-bound
-        super_mclass = system_class.get_class()
+        super_mclass = system_class.get_class(self._universe.nilObject)
         super_mclass.set_instance_invokables(self._universe.new_array_from_list(self._class_methods))
         super_mclass.set_instance_fields(self._universe.new_array_from_list(self._class_fields))

src/som/compiler/disassembler.py

-from som.vm.universe import error_print, error_println
+from som.vm.universe import error_print, error_println, get_current
 from som.interpreter.bytecodes import bytecode_as_str, bytecode_length, Bytecodes
 
 def dump(clazz):
@@ -61,7 +61,7 @@ def dump_method(m, indent):
             constant = m.get_constant(b)
             error_println("(index: " + str(m.get_bytecode(b + 1)) +
                                    ") value: (" + 
-                                   str(constant.get_class().get_name()) +
+                                   str(constant.get_class(get_current()).get_name()) +
                                    ") " + str(constant))
         elif bytecode == Bytecodes.push_global:
             error_println("(index: " + str(m.get_bytecode(b + 1)) +

src/som/compiler/method_generation_context.py

@@ -29,21 +29,13 @@ class MethodGenerationContext(object):
         return empty_primitive(self._signature.get_string(), universe)
 
     def assemble(self, universe):
-        # create a method instance with the given number of bytecodes and literals
-        num_literals = len(self._literals)
-        num_locals   = len(self._locals)
+        num_locals = len(self._locals)
         
         meth = universe.new_method(self._signature,
                                    len(self._bytecode),
-                                   num_literals,
+                                   self._literals,
                                    universe.new_integer(num_locals),
                                    universe.new_integer(self._compute_stack_depth()))
-
-        # copy literals into the method
-        i = 0
-        for l in self._literals:
-            meth.set_indexable_field(i, l)
-            i += 1
         
         # copy bytecodes into method
         i = 0

src/som/compiler/parser.py

@@ -89,7 +89,7 @@ class Parser(object):
         if super_name.get_string() != "nil":
             super_class = self._universe.load_class(super_name)
             cgenc.set_instance_fields_of_super(super_class.get_instance_fields())
-            cgenc.set_class_fields_of_super(super_class.get_class().get_instance_fields())
+            cgenc.set_class_fields_of_super(super_class.get_class(self._universe).get_instance_fields())
         else:
             # WARNING:
             # We hardcode here the field names for Class

src/som/vmobjects/frame.py → src/som/interpreter/frame.py

 from rpython.rlib import jit
-from som.vmobjects.array import Array
 
 # Frame layout:
 # 
@@ -12,128 +11,105 @@ from som.vmobjects.array import Array
 # | ...             |
 # +-----------------+
 #
-class Frame(Array):
-    
-    # Static field indices and number of frame fields
-    NUMBER_OF_FRAME_FIELDS = Array.NUMBER_OF_OBJECT_FIELDS
-    
-    _immutable_fields_ = ["_method", "_context"]
+class Frame(object):
+        
+    _immutable_fields_ = ["_method", "_context", "_stack"]
 
     def __init__(self, nilObject, num_elements, method, context, previous_frame):
-        Array.__init__(self, nilObject, num_elements)
-        self._stack_pointer  = 0
-        self._bytecode_index = 0
         self._method         = method
         self._context        = context
-        self._previous_frame = previous_frame if previous_frame else nilObject
+        self._stack          = [nilObject] * num_elements
+        self._stack_pointer  = 0
+        self._bytecode_index = 0
+        self._previous_frame = previous_frame
     
     def get_previous_frame(self):
-        # Get the previous frame by reading the field with previous frame index
         return self._previous_frame
 
-    def clear_previous_frame(self, nilObject):
-        # Set the previous frame to nil
-        self._previous_frame = nilObject
+    def clear_previous_frame(self):
+        self._previous_frame = None
 
-    def has_previous_frame(self, nilObject):
-        return self._previous_frame != nilObject
+    def has_previous_frame(self):
+        return self._previous_frame is not None
 
-    def is_bootstrap_frame(self, nilObject):
-        return not self.has_previous_frame(nilObject)
+    def is_bootstrap_frame(self):
+        return not self.has_previous_frame()
 
     def get_context(self):
-        # Get the context by reading the field with context index
         return self._context
 
-    def has_context(self, nilObject):
-        return self._context != nilObject
+    def has_context(self):
+        return self._context is not None
 
     @jit.unroll_safe
     def _get_context(self, level):
-        # Get the context frame at the given level
+        """ Get the context frame at the given level """
         frame = self
 
         # Iterate through the context chain until the given level is reached
         for _ in range(level, 0, -1):
-            # Get the context of the current frame
             frame = frame.get_context()
 
         # Return the found context
         return frame
 
     @jit.unroll_safe
-    def get_outer_context(self, nilObject):
-        # Compute the outer context of this frame
+    def get_outer_context(self):
+        """ Compute the outer context of this frame """
         frame = self
 
-        # Iterate through the context chain until null is reached
-        while frame.has_context(nilObject):
+        while frame.has_context():
             frame = frame.get_context()
 
         # Return the outer context
         return frame
 
     def get_method(self):
-        # Get the method by reading the field with method index
         return self._method
 
     def get_number_of_arguments(self):
-        return self.get_method().get_number_of_arguments()
-
-    def _get_default_number_of_fields(self):
-        # Return the default number of fields in a frame
-        return self.NUMBER_OF_FRAME_FIELDS
+        return self._method.get_number_of_arguments()
 
     def pop(self):
-        # Pop an object from the expression stack and return it
-        stack_pointer = self.get_stack_pointer()
-        self.set_stack_pointer(stack_pointer - 1)
-        return self.get_indexable_field(stack_pointer)
+        """ Pop an object from the expression stack and return it """
+        stack_pointer = self._stack_pointer
+        self._stack_pointer = stack_pointer - 1
+        return self._stack[stack_pointer]
 
     def push(self, value):
-        # Push an object onto the expression stack
-        stack_pointer = self.get_stack_pointer() + 1
-        self.set_indexable_field(stack_pointer, value)
-        self.set_stack_pointer(stack_pointer)
-
-    def get_stack_pointer(self):
-        # Get the current stack pointer for this frame
-        return jit.promote(self._stack_pointer)
-
-    def set_stack_pointer(self, value):
-        # Set the current stack pointer for this frame
-        self._stack_pointer = value
+        """ Push an object onto the expression stack """
+        stack_pointer = self._stack_pointer + 1
+        self._stack[stack_pointer] = value
+        self._stack_pointer = stack_pointer
 
     def reset_stack_pointer(self):
+        """ Set the stack pointer to its initial value thereby clearing
+            the stack """
         # arguments are stored in front of local variables
-
-        # Set the stack pointer to its initial value thereby clearing the stack
-        self.set_stack_pointer(self.get_number_of_arguments() +
+        self._stack_pointer = (self.get_number_of_arguments() +
                 self.get_method().get_number_of_locals().get_embedded_integer() - 1)
 
     def get_bytecode_index(self):
-        # Get the current bytecode index for this frame
         return self._bytecode_index
 
     def set_bytecode_index(self, value):
-        # Set the current bytecode index for this frame
         self._bytecode_index = value
 
     def get_stack_element(self, index):
         # Get the stack element with the given index
         # (an index of zero yields the top element)
-        return self.get_indexable_field(self.get_stack_pointer() - index)
+        return self._stack[self._stack_pointer - index]
 
     def set_stack_element(self, index, value):
         # Set the stack element with the given index to the given value
         # (an index of zero yields the top element)
-        self.set_indexable_field(self.get_stack_pointer() - index, value)
+        self._stack[self._stack_pointer - index] = value
 
     def _get_local(self, index):
-        return self.get_indexable_field(self.get_number_of_arguments() + index)
+        return self._stack[self.get_number_of_arguments() + index]
 
     def _set_local(self, index, value):
-        self.set_indexable_field(self.get_number_of_arguments() + index, value)
+        self._stack[self.get_number_of_arguments() + index] = value
 
     def get_local(self, index, context_level):
         # Get the local with the given index in the given context
@@ -149,14 +125,14 @@ class Frame(Array):
         context = self._get_context(context_level)
 
         # Get the argument with the given index
-        return context.get_indexable_field(index)
+        return context._stack[index]
 
     def set_argument(self, index, context_level, value):
         # Get the context
         context = self._get_context(context_level)
 
         # Set the argument with the given index to the given value
-        context.set_indexable_field(index, value)
+        context._stack[index] = value
 
     @jit.unroll_safe
     def copy_arguments_from(self, frame):
@@ -165,7 +141,7 @@ class Frame(Array):
         # - copy them into the argument area of the current frame
         num_args = self.get_method().get_number_of_arguments()
         for i in range(0, num_args):
-            self.set_indexable_field(i, frame.get_stack_element(num_args - 1 - i))
+            self._stack[i] = frame.get_stack_element(num_args - 1 - i)
 
     def print_stack_trace(self, nilObject):
         # Print a stack trace starting in this frame
@@ -174,5 +150,5 @@ class Frame(Array):
         std_println(" %d @ %s" % (self.get_bytecode_index(),
                              self.get_method().get_signature().get_string()))
         
-        if self.has_previous_frame(nilObject):
-            self.get_previous_frame().print_stack_trace(nilObject)
+        if self.has_previous_frame():
+            self.get_previous_frame().print_stack_trace()

src/som/interpreter/interpreter.py

 from som.interpreter.bytecodes import bytecode_length, Bytecodes
+from som.vmobjects.clazz import Class
 
 from rpython.rlib import jit
 
@@ -122,16 +123,16 @@ class Interpreter(object):
         result = frame.pop()
 
         # Compute the context for the non-local return
-        context = frame.get_outer_context(self._universe.nilObject)
+        context = frame.get_outer_context()
 
         # Make sure the block context is still on the stack
-        if not context.has_previous_frame(self._universe.nilObject):
+        if not context.has_previous_frame():
             # Try to recover by sending 'escapedBlock:' to the sending object
             # this can get a bit nasty when using nested blocks. In this case
             # the "sender" will be the surrounding block and not the object
             # that actually sent the 'value' message.
             block  = frame.get_argument(0, 0)
-            sender = frame.get_previous_frame().get_outer_context(self._universe.nilObject).get_argument(0, 0)
+            sender = frame.get_previous_frame().get_outer_context().get_argument(0, 0)
 
             # pop the frame of the currently executing block...
             self._pop_frame()
@@ -141,7 +142,7 @@ class Interpreter(object):
             return
 
         # Unwind the frames
-        while self.get_frame() != context:
+        while self.get_frame() is not context:
             self._pop_frame()
 
         # Pop the top frame and push the result
@@ -158,7 +159,7 @@ class Interpreter(object):
         receiver = frame.get_stack_element(num_args - 1)
 
         # Send the message
-        self._send(signature, receiver.get_class(), bytecode_index)
+        self._send(signature, receiver.get_class(self._universe), bytecode_index)
 
 
     def start(self):
@@ -241,7 +242,7 @@ class Interpreter(object):
 
     def get_self(self):
         # Get the self object from the interpreter
-        return self.get_frame().get_outer_context(self._universe.nilObject).get_argument(0, 0)
+        return self.get_frame().get_outer_context().get_argument(0, 0)
 
     def _send(self, selector, receiver_class, bytecode_index):
         # First try the inline cache
@@ -283,7 +284,7 @@ class Interpreter(object):
         self.set_frame(self._frame.get_previous_frame())
 
         # Destroy the previous pointer on the old top frame
-        result.clear_previous_frame(self._universe.nilObject)
+        result.clear_previous_frame()
 
         # Return the popped frame
         return result

src/som/primitives/class_primitives.py

@@ -6,6 +6,26 @@ def _new(ivkbl, frame, interpreter):
     rcvr = frame.pop()
     frame.push(interpreter.get_universe().new_instance(rcvr))
 
+def _name(ivkbl, frame, interpreter):
+    rcvr = frame.pop()
+    frame.push(rcvr.get_name())
+
+def _super_class(ivkbl, frame, interpreter):
+    rcvr = frame.pop()
+    frame.push(rcvr.get_super_class())
+
+def _methods(ivkbl, frame, interpreter):
+    rcvr = frame.pop()
+    frame.push(rcvr.get_instance_invokables())
+    
+def _fields(ivkbl, frame, interpreter):
+    rcvr = frame.pop()
+    frame.push(rcvr.get_instance_fields())
+
 class ClassPrimitives(Primitives):
     def install_primitives(self):
-        self._install_instance_primitive(Primitive("new", self._universe, _new))
\ No newline at end of file
+        self._install_instance_primitive(Primitive("new",        self._universe, _new))
+        self._install_instance_primitive(Primitive("name",       self._universe, _name))
+        self._install_instance_primitive(Primitive("superclass", self._universe, _super_class))
+        self._install_instance_primitive(Primitive("methods",    self._universe, _methods))
+        self._install_instance_primitive(Primitive("fields",     self._universe, _fields))

src/som/primitives/method_primitives.py

+from som.primitives.primitives import Primitives
+from som.vmobjects.primitive   import Primitive 
+
+def _holder(ivkbl, frame, interpreter):
+    rcvr = frame.pop()
+    frame.push(rcvr.get_holder())
+
+def _signature(ivkbl, frame, interpreter):
+    rcvr = frame.pop()
+    frame.push(rcvr.get_signature())
+
+class MethodPrimitives(Primitives):
+    def install_primitives(self):
+        self._install_instance_primitive(Primitive("holder",    self._universe, _holder))
+        self._install_instance_primitive(Primitive("signature", self._universe, _signature))

src/som/primitives/object_primitives.py

@@ -2,6 +2,7 @@ from rpython.rlib.objectmodel import compute_identity_hash
 
 from som.primitives.primitives import Primitives
 
+from som.vmobjects.object    import Object  
 from som.vmobjects.primitive import Primitive
 from som.vmobjects.array     import Array 
 
@@ -20,9 +21,12 @@ def _hashcode(ivkbl, frame, interpreter):
 
 def _objectSize(ivkbl, frame, interpreter):
     rcvr = frame.pop()
-    size = rcvr.get_number_of_fields()
-    if isinstance(rcvr, Array):
-        size += rcvr.get_number_of_indexable_fields()
+    size = 0
+    
+    if isinstance(rcvr, Object):
+        size = rcvr.get_number_of_fields()
+    elif isinstance(rcvr, Array):
+        size = rcvr.get_number_of_indexable_fields()
 
     frame.push(interpreter.get_universe().new_integer(size))
 
@@ -30,7 +34,7 @@ def _perform(ivkbl, frame, interpreter):
     selector = frame.pop()
     rcvr     = frame.get_stack_element(0)
 
-    invokable = rcvr.get_class().lookup_invokable(selector)
+    invokable = rcvr.get_class(interpreter.get_universe()).lookup_invokable(selector)
     invokable.invoke(frame, interpreter)
 
 def _performInSuperclass(ivkbl, frame, interpreter):
@@ -49,7 +53,7 @@ def _performWithArguments(ivkbl, frame, interpreter):
     for i in range(0, args.get_number_of_indexable_fields()):
         frame.push(args.get_indexable_field(i))
 
-    invokable = rcvr.get_class().lookup_invokable(selector)
+    invokable = rcvr.get_class(interpreter.get_universe()).lookup_invokable(selector)
     invokable.invoke(frame, interpreter)
 
 def _instVarAt(ivkbl, frame, interpreter):
@@ -71,7 +75,7 @@ def _halt(ivkbl, frame, interpreter):
 
 def _class(ivkbl, frame, interpreter):
     rcvr = frame.pop()
-    frame.push(rcvr.get_class())
+    frame.push(rcvr.get_class(interpreter.get_universe()))
     
 
 

src/som/primitives/primitive_primitives.py

+from som.primitives.primitives import Primitives
+from som.vmobjects.primitive   import Primitive 
+
+def _holder(ivkbl, frame, interpreter):
+    rcvr = frame.pop()
+    frame.push(rcvr.get_holder())
+
+def _signature(ivkbl, frame, interpreter):
+    rcvr = frame.pop()
+    frame.push(rcvr.get_signature())
+
+class PrimitivePrimitives(Primitives):
+    def install_primitives(self):
+        self._install_instance_primitive(Primitive("holder",    self._universe, _holder))
+        self._install_instance_primitive(Primitive("signature", self._universe, _signature))

src/som/primitives/primitives.py

@@ -21,4 +21,4 @@ class Primitives(object):
     def _install_class_primitive(self, primitive):
         # Install the given primitive as an instance primitive in the class of
         # the holder class
-        self._holder.get_class().add_instance_primitive(primitive)
+        self._holder.get_class(self._universe).add_instance_primitive(primitive)

src/som/primitives/string_primitives.py

@@ -20,11 +20,12 @@ def _length(ivkbl, frame, interpreter):
 def _equals(ivkbl, frame, interpreter):
     op1 = frame.pop()
     op2 = frame.pop() # rcvr
-    if op1.get_class() == interpreter.get_universe().stringClass:
+    universe = interpreter.get_universe()
+    if op1.get_class(universe) == universe.stringClass:
         if op1.get_embedded_string() == op2.get_embedded_string():
-            frame.push(interpreter.get_universe().trueObject)
+            frame.push(universe.trueObject)
             return
-    frame.push(interpreter.get_universe().falseObject)
+    frame.push(universe.falseObject)
 
 def _substring(ivkbl, frame, interpreter):
     end   = frame.pop()

src/som/vm/shell.py

@@ -20,7 +20,7 @@ class Shell(object):
         std_println("SOM Shell. Type \"quit\" to exit.\n");
 
         # Create a fake bootstrap frame
-        current_frame = self._interpreter.push_new_frame(self._bootstrap_method, self._universe.nilObject)
+        current_frame = self._interpreter.push_new_frame(self._bootstrap_method, None)
 
         # Remember the first bytecode index, e.g. index of the halt instruction
         bytecode_index = current_frame.get_bytecode_index()

src/som/vmobjects/abstract_object.py

+class AbstractObject(object):
+        
+    def send(self, selector_string, arguments, universe, interpreter):
+        # Turn the selector string into a selector
+        selector = universe.symbol_for(selector_string)
+
+        # Push the receiver onto the stack
+        interpreter.get_frame().push(self)
+
+        # Push the arguments onto the stack
+        for arg in arguments:
+            interpreter.get_frame().push(arg)
+
+        # Lookup the invokable
+        invokable = self.get_class(universe).lookup_invokable(selector)
+
+        # Invoke the invokable
+        invokable.invoke(interpreter.get_frame(), interpreter)
+
+    def send_does_not_understand(self, selector, universe, interpreter):
+        # Compute the number of arguments
+        number_of_arguments = selector.get_number_of_signature_arguments()
+
+        frame = interpreter.get_frame()
+        frame.print_stack_trace(universe.nilObject)
+
+        # Allocate an array with enough room to hold all arguments
+        arguments_array = universe.new_array_with_length(number_of_arguments)
+
+        # Remove all arguments and put them in the freshly allocated array
+        i = number_of_arguments - 1
+        
+        while i >= 0:
+            arguments_array.set_indexable_field(i, frame.pop())
+            i -= 1
+            
+        args = [selector, arguments_array]
+        self.send("doesNotUnderstand:arguments:", args, universe, interpreter)
+
+    def send_unknown_global(self, global_name, universe, interpreter):
+        arguments = [global_name]
+        self.send("unknownGlobal:", arguments, universe, interpreter)
+
+    def send_escaped_block(self, block, universe, interpreter):
+        arguments = [block]
+        self.send("escapedBlock:", arguments, universe, interpreter)
+
+    def get_class(self, universe):
+        raise NotImplementedError("Subclasses need to implement get_class(universe).")
+
+    def is_invokable(self):
+        return False
+
+    def __str__(self):
+        from som.vm.universe import get_current
+        return "a " + self.get_class(get_current()).get_name().get_string()

src/som/vmobjects/array.py

-from som.vmobjects.object import Object
+from som.vmobjects.abstract_object import AbstractObject
 
-class Array(Object):
+class Array(AbstractObject):
 
     _immutable_fields_ = ["_indexable_fields"]
     
     def __init__(self, nilObject, number_of_indexable_fields):
-        Object.__init__(self, nilObject)
+        AbstractObject.__init__(self)
         
         # Private array of indexable fields
         self._indexable_fields = [nilObject] * number_of_indexable_fields
@@ -41,3 +41,6 @@ class Array(Object):
         # Copy all indexable fields from this array to the destination array
         for i in range(self.get_number_of_indexable_fields()):
             destination.set_indexable_field(i, self.get_indexable_field(i))
+
+    def get_class(self, universe):
+        return universe.arrayClass

src/som/vmobjects/biginteger.py

-from som.vmobjects.object import Object
+from som.vmobjects.abstract_object import AbstractObject
 
-class BigInteger(Object):
+class BigInteger(AbstractObject):
 
     _immutable_fields_ = ["_embedded_biginteger"]
 
-    def __init__(self, nilObject, value):
-        Object.__init__(self, nilObject)
+    def __init__(self, value):
+        AbstractObject.__init__(self)
         self._embedded_biginteger = value
     
     def get_embedded_biginteger(self):
@@ -14,3 +14,6 @@ class BigInteger(Object):
     def get_embedded_value(self):
         """This Method is polymorphic with Integer"""
         return self._embedded_biginteger
+    
+    def get_class(self, universe):
+        return universe.bigintegerClass

src/som/vmobjects/block.py

 from rpython.rlib import jit
 
-from som.vmobjects.object    import Object
+from som.vmobjects.abstract_object import AbstractObject
 from som.vmobjects.primitive import Primitive
 
-class Block(Object):
-    
-    NUMBER_OF_BLOCK_FIELDS = Object.NUMBER_OF_OBJECT_FIELDS
+class Block(AbstractObject):
     
     _immutable_fields_ = ["_method", "_context"]
     
-    def __init__(self, nilObject, method, context):
-        Object.__init__(self, nilObject)
-        self._number_of_arguments = 0
+    def __init__(self, method, context):
+        AbstractObject.__init__(self)
         self._method  = method
         self._context = context
         
     def get_method(self):
-        # Get the method of this block by reading the field with method index
         return jit.promote(self._method)
     
     def get_context(self):
-        # Get the context of this block by reading the field with context index
         return self._context
-
-    def _get_default_number_of_fields(self):
-        # Return the default number of fields for a block
-        return self.NUMBER_OF_BLOCK_FIELDS
+    
+    def get_class(self, universe):
+        return universe.blockClasses[self._method.get_number_of_arguments()]
   
     class Evaluation(Primitive):
         _immutable_fields_ = ['_number_of_arguments']

src/som/vmobjects/clazz.py

 from som.vmobjects.object      import Object
-from som.primitives.primitives import Primitives
 
 class Class(Object):
     
-    # Static field indices and number of class fields
-    SUPER_CLASS_INDEX         = Object.NUMBER_OF_OBJECT_FIELDS
-    NAME_INDEX                = 1 + SUPER_CLASS_INDEX
-    INSTANCE_FIELDS_INDEX     = 1 + NAME_INDEX
-    INSTANCE_INVOKABLES_INDEX = 1 + INSTANCE_FIELDS_INDEX
-    NUMBER_OF_CLASS_FIELDS    = 1 + INSTANCE_INVOKABLES_INDEX
-
+    _immutable_fields_ = ["_super_class"
+                          "_name",
+                          "_instance_fields"
+                          "_instance_invokables"]
     
     def __init__(self, universe, number_of_fields=-1):
         Object.__init__(self, universe.nilObject, number_of_fields)
+        self._super_class = universe.nilObject
+        self._name        = None
+        self._instance_fields = None
+        self._instance_invokables = None
         self._invokables_table = {}
         self._universe = universe
         
     def get_super_class(self):
-        # Get the super class by reading the field with super class index
-        return self.get_field(self.SUPER_CLASS_INDEX)
+        return self._super_class
 
     def set_super_class(self, value):
-        # Set the super class by writing to the field with super class index
-        self.set_field(self.SUPER_CLASS_INDEX, value)
+        self._super_class = value
     
     def has_super_class(self):
-        # Check whether or not this class has a super class
-        return self.get_field(self.SUPER_CLASS_INDEX) != self._universe.nilObject
+        return self._super_class is not self._universe.nilObject
 
     def get_name(self):
-        # Get the name of this class by reading the field with name index
-        return self.get_field(self.NAME_INDEX)
+        return self._name
   
     def set_name(self, value):
-        # Set the name of this class by writing to the field with name index
-        self.set_field(self.NAME_INDEX, value)
+        self._name = value
 
     def get_instance_fields(self):
-        # Get the instance fields by reading the field with the instance fields index
-        return self.get_field(self.INSTANCE_FIELDS_INDEX)
+        return self._instance_fields
 
     def set_instance_fields(self, value):
-        # Set the instance fields by writing to the field with the instance fields index
-        self.set_field(self.INSTANCE_FIELDS_INDEX, value)
+        self._instance_fields = value
   
     def get_instance_invokables(self):
-        # Get the instance invokables by reading the field with the instance
-        # invokables index
-        return self.get_field(self.INSTANCE_INVOKABLES_INDEX)
-
+        return self._instance_invokables
  
     def set_instance_invokables(self, value):
-        # Set the instance invokables by writing to the field with the instance
-        # invokables index
-        self.set_field(self.INSTANCE_INVOKABLES_INDEX, value)
+        self._instance_invokables = value
  
         # Make sure this class is the holder of all invokables in the array
         for i in range(0, self.get_number_of_instance_invokables()):
@@ -62,24 +50,18 @@ class Class(Object):
             invokable.set_holder(self)
     
     def get_number_of_instance_invokables(self):
-        # Return the number of instance invokables in this class
+        """ Return the number of instance invokables in this class """
         return self.get_instance_invokables().get_number_of_indexable_fields()
   
     def get_instance_invokable(self, index):
-        # Get the instance invokable with the given index
+        """ Get the instance invokable with the given index """
         return self.get_instance_invokables().get_indexable_field(index)