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Simple Calculator

Narendra kadimetla
Greenhorn

Joined: Mar 12, 2010
Posts: 1
I am new to JAVA.I was asked to build a simple Add class and i did it this way..



He then asked me to do Subtraction,Multiplication and Divison.I did them.
Now he wants me build a simple calculator using all these classes.
I am not getting anything...please help me...


Naren Reddy.
Greg Stevens
Ranch Hand

Joined: Jul 23, 2009
Posts: 41
What would the interface for the Add class be? How would you use an object of type Add?
Devaka Cooray
ExamLab Creator
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Joined: Jul 29, 2008
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  40

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Campbell Ritchie
Sheriff

Joined: Oct 13, 2005
Posts: 38851
    
  23
You need to pass values to the add method, and that returns a result.

Are you sure you should have an Add class, rather than an Arithmetic class with a (static) add method?
Matt Cartwright
Ranch Hand

Joined: Aug 25, 2008
Posts: 149

Campbell Ritchie wrote:You need to pass values to the add method, and that returns a result.

Are you sure you should have an Add class, rather than an Arithmetic class with a (static) add method?


This is definitely the way to go for all of your supported calculator operations.

Reorganizing the stack from the user input can be quite tricky though when using
infix notation. It might be a lot easier to enhance functionality step by step using
Reverse Polish Notation (RPN) internally.
You might wanna have a look here.

Good luck and please keep us posted
Matt
Campbell Ritchie
Sheriff

Joined: Oct 13, 2005
Posts: 38851
    
  23
Is reverse Polish notation the same as postfix notation? Agree it is better, but it requires parsing skills, so it may be difficult to implement.
Matt Cartwright
Ranch Hand

Joined: Aug 25, 2008
Posts: 149

Campbell Ritchie wrote:Is reverse Polish notation the same as postfix notation? Agree it is better, but it requires parsing skills, so it may be difficult to implement.

that's affirmative.

Postfix notation is just another name for RPN.

Regarding the parsing:

from my point of view it is much more difficult to
parse the entire infix statement than just stack
RPN instructions.

Just an opinion.

Matt
Campbell Ritchie
Sheriff

Joined: Oct 13, 2005
Posts: 38851
    
  23
Agree it is much easier to put postfix/reverse Polish onto a stack, which I am doing myself in FORTH, but it does mean learning notation like 1 2 3 * + instead of 1 + 2 * 3. When I said "parsing skills" I thought Narendra kadimetla wanted to start with an infix expression (eg 1 + 2 * 3) and evaluate that correctly. When you said
quite tricky though when using infix notation
you must have been thinking on the same lines.
 
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subject: Simple Calculator