operators
Class PSIndex

java.lang.Object
  operators.PSIndex

All Implemented Interfaces:

PSObject, PSOperator, PSStackOperator

public class PSIndex

extends java.lang.Object

implements PSStackOperator

Implements PSStackOperator interface.

Methods such as getOperatorToken() are inherited by PSStackOperator interface which in turn, are inherited by PSOperator.This concrete class is responsible for the copy of the n-element on top of the stack.

Constructor Summary

PSIndex()

Method Summary

void	action(PSStack s) Copies of the n-element on top of the stack.
java.lang.String	getOperatorToken() Returns the token identifying this operator.
boolean	isValid(PSStack s) Checks if it valid to use this operator now.

Methods inherited from class java.lang.Object

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

Constructor Detail

PSIndex

public PSIndex()

Method Detail

getOperatorToken

public java.lang.String getOperatorToken()

Returns the token identifying this operator.

Returns the name of the operand that this concrete class simulates,here "index".

Precondition : A valid operator class has been created.
Postcondition : A string is returned,labeling the semantics of this class.

Specified by:

getOperatorToken in interface PSOperator

Returns:

The token identifying this operator.

isValid

public boolean isValid(PSStack s)
                throws PSSyntaxException

Checks if it valid to use this operator now.

Check if the copy of the i-element on top of the stack can be made.

Precondition : A valid instance of PSStack is given.
Postcondition : A reply to whether the elements of the stack can be removed.

Specified by:

isValid in interface PSOperator

Parameters:

s - A reference to a PSStack instance.

Returns:

True if the operation can be performed,false otherwise.

Throws:

PSSyntaxException - The syntax of the token is wrong.

action

public void action(PSStack s)

Copies of the n-element on top of the stack.

Precondition : A valid stack is given to method.
Postcondition : A copy of the n-element on top of the stack.

Specified by:

action in interface PSStackOperator

Parameters:

s - The Run-time Stack where the elements are stored.