com.pdmfc.tea.runtime
Class SContext

java.lang.Object
  com.pdmfc.tea.runtime.SContext

Direct Known Subclasses:

STeaRuntime

public class SContext
extends java.lang.Object

Represents a context inside which variables are created and commands executed. Contexts form an hierarchy, where child contexts hide variables defined in parent contexts. A context with no parent is a toplevel context.

Constructor Summary

protected	SContext() Initializes a top level context.
protected	SContext(int initialCapacity) Initializes a top level context with a particular initial capacity.
	SContext(SContext parent) Initializes a context descending from parent.

Method Summary

protected void	clearAll() Forgets all the variables.
SContext	clone(SContext parent)
SContext	getParent() Retrives the parent context.
java.lang.Object	getVar(SObjSymbol name) Obtains the contents of the variable associated with symbol name.
SObjVar	getVarObject(SObjSymbol name) Obtains the contents of the variable associated with symbol name.
boolean	isDefined(SObjSymbol name) Checks if a given variable is defined in this context.
SContext	newChild() Creates a new context having this context for parent.
SObjVar	newVar(SObjSymbol name, java.lang.Object value) Creates a new variable inside this context.
SObjVar	newVar(java.lang.String name, java.lang.Object value) Creates a new variable inside this context.
void	setVar(SObjSymbol name, java.lang.Object value) Sets the contents of a variable previously created.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

SContext

protected SContext()

Initializes a top level context.

SContext

public SContext(SContext parent)

Initializes a context descending from parent. Variables defined inside this context hide variables with the same name inside context. If parent is null then this will be a top-level context.

Parameters:

parent - The parent context of this one. It will be null in the case of a top level context.

SContext

protected SContext(int initialCapacity)

Initializes a top level context with a particular initial capacity.

Parameters:

initialCapacity - The internal hashtable initial capacity.

Method Detail

newChild

public SContext newChild()

Creates a new context having this context for parent.

Returns:

A newly created context.

clone

public SContext clone(SContext parent)

getParent

public SContext getParent()

Retrives the parent context. In the case of a toplevel context the parent context is not set.

Returns:

The parent context. It will be null in the case of a toplevel context.

clearAll

protected void clearAll()

Forgets all the variables.

newVar

public final SObjVar newVar(java.lang.String name,
                            java.lang.Object value)

Creates a new variable inside this context. The variable will be associated with a symbol named name and it will have has contents the object referenced by value.

Parameters:

name - The name of the symbol to be associated to the variable being created.

value - Reference to the object to be stored inside the variable.

isDefined

public final boolean isDefined(SObjSymbol name)

Checks if a given variable is defined in this context. The variable is also searched in all parent contexts.

Parameters:

name - The symbol associated with the variable being checked for existence.

Returns:

True if the variable is defined in this context or in some of its parent contexts. False otherwise.

newVar

public final SObjVar newVar(SObjSymbol name,
                            java.lang.Object value)

Creates a new variable inside this context. The variable will be associated with symbol name and it will have has contents the object referenced by value.

Parameters:

name - Symbol to be associated to the variable being created.

setVar

public final void setVar(SObjSymbol name,
                         java.lang.Object value)
                  throws SNoSuchVarException

Sets the contents of a variable previously created. After this method returns variable name will have as contents a reference to object value.

Parameters:

name - Symbol associated with the variable to be set.

value - Object to store in the variable.

Throws:

SNoSuchVarException - Throw if no variable name was previously created.

getVar

public final java.lang.Object getVar(SObjSymbol name)
                              throws SNoSuchVarException

Obtains the contents of the variable associated with symbol name. If such a variable does not exist in this context then it is searched in its parent.

Parameters:

name - Symbol associated with the variable whose contents are to be retrieved.

Returns:

The object in the variable associated with symbol name.

Throws:

SNoSuchVarException - Thrown if the variable does not exist neither in this context nor in any of the contexts up the hierarchy.

getVarObject

public final SObjVar getVarObject(SObjSymbol name)
                           throws SNoSuchVarException

Obtains the contents of the variable associated with symbol name. If such a variable does not exist in this context then it is searched in its parent.

Parameters:

name - Symbol associated with the variable whose contents are to be retrieved.

Returns:

The object in the variable associated with symbol name.

Throws:

SNoSuchVarException - Thrown if the variable does not exist neither in this context nor in any of the contexts up the hierarchy.