mithun3 / rpn-calculator

Reverse Polish Notation Calculator

Reverse Polish notation (RPN), also known as Polish postfix notation or simply postfix notation, is a mathematical notation in which operators follow their operands. RPN - Wiki

Requirements

• The calculator has a stack that can contain real numbers.
• The calculator waits for user input and expects to receive strings containing whitespace separated lists of numbers and operators.
• Numbers are pushed on to the stack. Operators operate on numbers that are on the stack.
• Available operators are +, -, *, /, sqrt, undo, clear
• Operators pop their parameters off the stack, and push their results back onto the stack.
• The 'clear' operator removes all items from the stack.
• The 'undo' operator undoes the previous operation. "undo undo" will undo the previous two operations.
• sqrt performs a square root on the top item from the stack
• The '+', '-', '*', '/' operators perform addition, subtraction, multiplication and division respectively on the top two items from the stack.
• After processing an input string, the calculator displays the current contents of the stack as a space-separated list.
• Numbers should be stored on the stack to at least 15 decimal places of precision, but displayed to 10 decimal places (or less if it causes no loss of precision).
• All numbers should be formatted as plain decimal strings (ie. no engineering formatting).
• If an operator cannot find a sufficient number of parameters on the stack, a warning is displayed: operator (position: ): insufficient parameters
• After displaying the warning, all further processing of the string terminates and the current state of the stack is displayed.

Example:

Enter your expression to be evaluated :
5 2
Stack : [5.0, 2.0]
clear
Stack : [Empty Stack]
2 sqrt
Stack : [1.4142135623730951]
clear
Stack : [Empty Stack]
5 2 -
Stack : [3.0]
clear
Stack : [Empty Stack]
5 4 3 2
Stack : [5.0, 4.0, 3.0, 2.0]
undo undo *
Stack : [20.0]
5 *
Stack : [100.0]

If there is an exception:

1 2 3 * 5 + * * 6 5
operator * (position: 8): insufficient parameters
Stack : [11.0]
(the 6 and 5 were not pushed on to the stack due to the previous error)

Getting Started

Prerequisites

Java 8 Maven 3.5.3

Setup & Running the application

Through Command Line

Run the following maven commands to get started

To download and install all dependencies:

mvn clean install -DskipTests

Run the tests:

mvn clean test

Run the application (main method):

mvn exec:java

Through Eclipse

• Open eclipse.
• Click File > Import.
• Type Maven in the search box under Select an import source:
• Select Existing Maven Projects.
• Click Next.
• Click Browse and select the folder that is the root of the Maven project (probably contains the pom.xml file)
• Click Next.
• Click Finish.