pkg15.pkg121project1

Class RPNCalc

java.lang.Object

pkg15.pkg121project1.RPNCalc

public class RPNCalc
extends java.lang.Object

RPNCalc is composed of a Stack object (with one of three implementations). RPNCalc also contains a TreeMap from java.util. The stack holds java objects. These objects may be of type Double or of type String. If the stack object is of type String, then the Object represents a variable name within the TreeMap. The TreeMap maps variable names to Floats. All of the names within the TreeMap are unique names.

Constructor Summary

Constructors

Constructor and Description
RPNCalc() Get a stack (one of three implementations) from the stack factory.

Method Summary

Modifier and Type	Method and Description
void	add() The operation removes two objects from the stack.
void	assign() The operation removes two objects from the stack.
boolean	calcNotEmpty() pre: none post: tells us if the calculator has an empty stack.
void	divide() The operation removes two objects from the stack.
static void	main(java.lang.String[] a) This main routine is used for testing the RPNCalc.
void	multiply() The operation removes two objects from the stack.
void	number(java.lang.Object item) Pre: there is room in the calculator's stack.
java.lang.Object	pop() This method always returns a value.
void	raise() The operation removes two objects from the stack.
void	subtract() The operation removes two objects from the stack.
java.lang.Object	top() Examine (but do not remove) the top value of the calculator's stack.

Methods inherited from class java.lang.Object

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

Constructor Detail

RPNCalc

public RPNCalc()

Get a stack (one of three implementations) from the stack factory. Get a TreeMap from java.util.TreeMap Pre: None Post: Stack and TreeMap are defined.

Method Detail

calcNotEmpty

public boolean calcNotEmpty()

pre: none post: tells us if the calculator has an empty stack.

add

public void add()

The operation removes two objects from the stack. If they are numbers then perform the operation and push the result back on the stack. If either or both are strings, get their values from the TreeMap, operate on these values and place the result back on the stack. pre: two objects exist on the top of the stack. Any names on the stack are reflected in the TreeMap. post: The operation was performed and the stack top has the result.

raise

public void raise()

The operation removes two objects from the stack. If they are numbers then perform the operation and push the result back on the stack. If either or both are strings, get their values from the TreeMap, operate on these values and place the result back on the stack. pre: two objects exist on the top of the stack. Any names on the stack are reflected in the TreeMap. post: The operation was performed and the stack top has the result.

subtract

public void subtract()

The operation removes two objects from the stack. If they are numbers then perform the operation and push the result back on the stack. If either or both are strings, get their values from the TreeMap, operate on these values and place the result back on the stack. pre: two objects exist on the top of the stack. Any names on the stack are reflected in the TreeMap. post: The operation was performed and the stack top has the result.

divide

public void divide()

The operation removes two objects from the stack. If they are numbers then perform the operation and push the result back on the stack. If either or both are strings, get their values from the TreeMap, operate on these values and place the result back on the stack. pre: two objects exist on the top of the stack. Any names on the stack are reflected in the TreeMap. post: The operation was performed and the stack top has the result.

multiply

public void multiply()

The operation removes two objects from the stack. If they are numbers then perform the operation and push the result back on the stack. If either or both are strings, get their values from the TreeMap, operate on these values and place the result back on the stack. pre: two objects exist on the top of the stack. Any names on the stack are reflected in the TreeMap. post: The operation was performed and the stack top has the result.

number

public void number(java.lang.Object item)

Pre: there is room in the calculator's stack. post: a new item has been added to the top of the stack.

assign

public void assign()

The operation removes two objects from the stack. The second to be removed must be a name of a variable. The first to be removed may be a name or a value. If it is a name, a table lookup is performed for its value. The operation adds a new name to the table with the value of the first object popped (this may have required a table lookup). If the name of this variable already exists in the table, it's old value is replaced with this new value. For example n 3 = assigns 3 to the variable n n 4 = replaces the 3 with a 4. k n = assigns 4 (the value of n) to k. pre: two objects must be available on the stack. The second is a name. post: the variable is assigned a new value in the TreeMap.

top

public java.lang.Object top()

Examine (but do not remove) the top value of the calculator's stack. pre: stack is not empty post: the value at the top is returned. If top is a variable, its value from the TreeMap is returned.

pop

public java.lang.Object pop()

This method always returns a value. If the stack has a name on the top, this name is dereferenced and the TreeMap is read for the value. Pre: stack is not empty Post: the stack is popped and the value is returned.

main

public static void main(java.lang.String[] a)

This main routine is used for testing the RPNCalc.