operators
Class PSGet

java.lang.Object
  operators.PSGet

All Implemented Interfaces:

PSObject, PSOperator, PSStringOperator

public class PSGet

extends java.lang.Object

implements PSStringOperator

Implements PSStringOperator interface.

Methods such as getOperatorToken() are inherited from PSStringOperator interface which, in turn, are inherited from PSOperator. This concrete class is responsible for returning the ascii value of the character at the position given on the string.

Constructor Summary

PSGet()

Method Summary

void	action(PSStack s) Returns the ascii value of the character at the position given on the string.
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

PSGet

public PSGet()

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 "get".

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.

The character can be returned if a valid string and an PSNumber are given with PSNumber <= length of string.

Precondition : A valid instance of PSStack with a PSString 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)

Returns the ascii value of the character at the position given on the string.

Precondition : A valid stack is given to method with a PSString and a PSNumber on top (PSNumber <= length of string).
Postcondition : The ascii value of the character will be pushed as a PSNumber to the stack.

Specified by:

action in interface PSStringOperator

Parameters:

s - The Runtime Stack which contains the string and position and will hold the ascii value.