____      _            _       _               _   ___  
  / ___|__ _| | ___ _   _| | __ _| |_ ___  _ __  / | / _ \ 
 | |   / _` | |/ __| | | | |/ _` | __/ _ \| '__| | || | | |
 | |__| (_| | | (__| |_| | | (_| | || (_) | |    | || |_| |
  \____\__,_|_|\___|\__,_|_|\__,_|\__\___/|_|    |_(_)___/ 
                                                           

The Calculator program allows users to perform basic arithmetic operations from the command line.  The invocation syntax is as follows:

     java Calculator COMMAND ARG_1 ARG_2 [ARG_3] ... [ARG_N]

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FEATURES
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Addition
--------
Feature: The program can be used to provide the sum of an arbitrary number of operands.  The command for performing addition is “--add”.  

    Scenario: Add two numbers together
        Given the command: --add
        And the arguments: 3 1.5
        When Calculator is executed
        Then “3.0 + 1.5 = 4.5” is displayed

    Scenario: Add more than two numbers together
        Given the command: --add
        And the arguments: 1.75 2 3.0 4 5.25
        When Calculator is executed
        Then “1.75 + 2.0 + 3.0 + 4.0 + 5.25 = 16.0” is displayed

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Subtraction
-----------
Feature: The program can be used to provide the difference between two numbers. The command for performing subtraction is “--sub”.  

    Scenario: Find the difference between two numbers
        Given the command: --sub
        And the arguments: 3 1.5
        When Calculator is executed
        Then “3.0 − 1.5 = 1.5” is displayed

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Multiplication
--------------
Feature: The program can be used to provide the product of an arbitrary number of operands.  The command for performing addition is “--mult”.  

    Scenario: Multiply two numbers together
        Given the command: --mult
        And the arguments: 5 1.5
        When Calculator is executed
        Then “5.0 × 1.5 = 7.5” is displayed

    Scenario: Multiply more than two numbers together
        Given the command: --mult
        And the arguments: 1.5 2 3.25
        When Calculator is executed
        Then “1.5 × 2 × 3.25 = 9.75” is displayed

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Division
--------
Feature: The program can be used to provide the quotient of two numbers. The command for performing division is “--div”.  

    Scenario: Find the quotient of two numbers
        Given the command: --sub
        And the arguments: 3 2.0
        When Calculator is executed
        Then “3.0 ÷ 2.0 = 1.5” is displayed

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Exponentiation
--------------
Feature: The program can be used to provide the value of a base number raised by an exponent.  The command for performing exponentiation is “--pow”.

    Scenario: Raise a base number by an exponent
        Given the command: --pow
        And the arguments: 3 2
        When Calculator is executed
        Then “3 raised to the power of 2 = 9” is displayed

    Scenario: Fractional exponents are not allowed
        Given the command: --pow
        And the arguments: 3 2.5
        When Calculator is executed
        Then “Error: Fractional exponents are not allowed” is displayed as an error

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Error Reporting
---------------
Feature: In order to make the program more user friendly, helpful feedback is provided when the user provides invalid input.  

    Scenario: An invalid number of arguments is provided for a command
        Given the command: <Command>
        And the invalid arguments: <Arguments>
        When Calculator is executed
        Then <Message> is displayed as an error

        Examples:
            | Command | Arguments | Message                                                              |
            | --add   | 1         | Usage: Calculator --add addend_1 addend_2 [addend_3] ... [addend_n]  |
            | --sub   | 1 2 3     | Usage: Calculator --sub minuend subtrahend                           |
            | --mult  | 7         | Usage: Calculator --mult factor_1 factor_2 [factor_3] ... [factor_N] |
            | --div   |           | Usage: Calculator --div dividend divisor                             |
            | --pow   | 4 5 6     | Usage: Calculator --pow base exponent                                |