operators
Class PSMoveto

java.lang.Object
  operators.PSMoveto

All Implemented Interfaces:

PSObject, PSOperator, PSPathOperator

public class PSMoveto

extends java.lang.Object

implements PSPathOperator

Implements PSPathOperator interface.

Methods such as getOperatorToken() are inherited from PSPathOperator interface which, in turn, are inherited from PSOperator. This concrete class is responsible for moving the "pen" to the coordinates given without drawing anything.

Before moving, action() has to check if there are 2 PSNumber literals on top of the Runtime Stack.

Constructor Summary

PSMoveto()

Method Summary

void	action(PSStack s, PSPath p) Updates the variables which hold the current position and the last move in the Graphics 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

PSMoveto

public PSMoveto()

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 "moveto".

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.

Moving the "pen" can occur if the coordinates have been given.

Precondition : A valid instance of PSStack is given with 2 PSNumber literals on top.
Postcondition : A reply to the question whether the operator can perfom its defined behaviour.

Specified by:

isValid in interface PSOperator

Parameters:

s - A reference to PSStack instance.

Returns:

True if the operation can be executed, false otherwise.

Throws:

PSSyntaxException - The syntax of the token is wrong.

action

public void action(PSStack s,
                   PSPath p)

Updates the variables which hold the current position and the last move in the Graphics Stack.

Precondition : A valid stack is given to method with 2 PSNumber literals on top.
Postcondition : The variable holding the current position will change to the coordinates given and the variable holding the last move will change to the new current position. (Note: the stack returns the y first).

Specified by:

action in interface PSPathOperator

Parameters:

s - The Runtime Stack which holds the coordinates.

p - The Graphics Stack.