operators
Class PSDeq

java.lang.Object
  operators.PSDeq

All Implemented Interfaces:

PSConsoleOperator, PSObject, PSOperator

public class PSDeq

extends java.lang.Object

implements PSConsoleOperator

Implements PSStackOperator interface.

Methods such as getOperatorToken() are inherited by PSConsoleOperator interface which in turn, are inherited by PSOperator.This concrete class is responsible for the printing of the toppest value in the output plus i'ts removal.

Constructor Summary

PSDeq()

Method Summary

void	action(PSStack s, java.io.OutputStream os) Prints of the toppest value in the output plus it removes it.
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

PSDeq

public PSDeq()

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 "==".

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 : At least one element must be inside the stack.
Postcondition : A reply to whether the 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,
                   java.io.OutputStream os)

Prints of the toppest value in the output plus it removes it.

Precondition : Prints of the toppest value in the output plus it removes it.
Postcondition : Printing and removing the top element of the stack.

Specified by:

action in interface PSConsoleOperator

Parameters:

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

os - The stream where the output will be directed.