A attribute object
is used to define additional properties of an object. The term attribute
is also used as a synonym for slot
referring to class defined properties.
A class is an object
that acts as a description of other objects called instances
of the class. Besides
various house-keeping information, a PCE class
describes the instance-variables
and methods of its instances.
defines a constant for all instances of the class. Class variables can
be used to define default values for an instance-variable.
Initial values for class-variables can be specified in the
file. See section 8.
A code object is an
object that represents a procedure. Code
objects are used for implementation of methods and to associate actions
with various events. For example a button object executes its associated
code object when depressed. The most typical code object is a message.
A control is a
standard GUI object
normally placed in dialog windows. Examples are buttons, text-entry
fields and menus.
An event is an object
that represents an activity of the user: mouse-movements, mouse-buttons,
- Forwarding of argument
When code objects are executed it is common to bind the var
objects @arg1, @arg2,
... to pass context information for the executing code. For example,
when a method object executes its code it will bind the arguments given
to the method to @arg1, ...
A function is a
subclass of class code
which yields a value when executed. The most important functions are
local variables (var), obtainers
and mathetical operations. They may be used as arguments to code
objects. They are executed when the code object is executed or when the
function needs to be converted to a type that does not accept a
- Get operation
Virtual machine operation to request information from some object.
Started by the Prolog predicate get/[3-13],
when an obtainer is executed or from PCE's built-in functionality.
Abbreviation for Graphical User Interface.
The sharing of definition from a super-class. When a PCE class
is created from a super-class
it is initially a copy of this
creation, instance variables and methods may be added and/or redefined.
Synonym for object,
often use to stress the fact that an object belongs to a particular
Placeholder for the local-state associated with an object.
is associated with a class and has a name and a type. Each of the instances
of the class defines a value for the instance variable. Instance
variables are represented by class
A message is an
object representing a send-operation.
The phrase ``sending a message to X'' is equivalent to ``invoking a get-
or send-operation on X''.
A method maps a selector
and a type vector onto an implementation which is either a C-function or
a code object. PCE
defines both get- and send-methods. If a send-operation
is invoked on an object, PCE will find a method associated with the
class of the object with a matching selector,
check the argument types and invoke the implementation of the method.
An object-reference is the identifier for a particular
instance. In Prolog object-references
are represented by
@Integer or @Atom.
An object is en entity
in PCE's world that is identified by an object-reference
and has a local state. An object is an
instance of a class.
The class defines both
the constituents of the local state as well as the operations (methods)
understood by the object.
An obtainer is a function
which invokes a get-operation
when evaluated. The class name is `?'.
object parses events
for a graphical object.
A selector is the
name of a send-operation
- Send Method
Refinement of method
that maps a send-operation
onto its implementation. See also Method
- Send operation
Virtual machine operation which invokes of a send-method
on some object. Started by the Prolog predicate send/[2-12],
when an message is
executed or from PCE's built-in functionality.
Equivalent to instance_variable.
The super-class of
a class serves as the
initial definition of a class.
See also inheritance.
User-defined subclass of class template. The refinements
introduced from template can be imported in another user-defined
class using the predicate use_class_template/1.
A var object is a function.
The commonly used vars
objects are: @arg1, ... (general
argument forwarding), @receiver
(receiver or a message), @event
(currently processes event object).