operators
Class PSPop

java.lang.Object
  operators.PSPop

All Implemented Interfaces:

PSObject, PSOperator, PSStackOperator

public class PSPop

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 removal of the toppset element found in stack.

Constructor Summary

PSPop()

Method Summary

void	action(PSStack s) Removes the toppest element of 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

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

Constructor Detail

PSPop

public PSPop()

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 "pop".

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 removal of the top element can be made.

Precondition : At least one element is inside the stack.
Postcondition : A reply to whether the toppest element 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)

Removes the toppest element of stack.

Precondition : At least one element is inside the stack.
Postcondition : The top element of the stack will be removed.

Specified by:

action in interface PSStackOperator

Parameters:

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