blog-rpncalc

Description

This project contains a set of JVM implementations of a simple reverse polish notation calculator. They were originally written as supporting materials for a discussion on the relationship between functional programming and the command pattern that I wrote for the KSM Partners blog. However, that blog has since changed its format, and KSM has graciously allowed me to re-home the articles myself.

• Part 0: Introduction
• Part 1: A Simple RPN Calcualtor in Java and the Command Pattern
• Part 2: Composite Commands
• Part 3: Implementing Undo
• Part 4: A Noun for State
• Part 5: Eliminating the Globals
• Part 6: Refactoring the REPL
• Part 7: Refactoring Loops with Reduce
• Part 8: Moving to Clojure
• Part 9: State and Commands in Clojure
• Part 10: Macros and the Intent of the Code

Because of the intent for this code to support a series of blog posts, the code is focused more on concision and readability than on robustness.

Project Structure

There are two top level sub-projects at the root of the distribution: java and clj. The java project contains the Java implementations of the calculator and is built with Maven. The clj project contains the Clojure implementations, and is built with Leiningen.

For both sub-projects, there is a top-level shell script, run.sh, that will build and then execute the project.

Java implemenations

• basic - A simple RPN calculator with support for the four basic mathematical operations and not much else.
• composite - basic extended with composite commands that can be composed of a sequence of other commands.
• undoable - composite extended with the ability to reverse the effects of a command that's already been executed.
• stateobject - undoable, with all calculator state moved into a first-class object.
• functional - stateobject without global variable.
• functionalrf - A minor refactoring of functional that simplifies command state management.
• reducer - A version of functionalrf that uses functional reduction to replace explicit looping.

Clojure implementations

• functionalrf - A reimplementation of the Java functionalrf build in Clojure.
• macro - functionalrf extended with a macro to automate generation of stack transformation commands.
• dfcompile - A version of macro that adds a simple compiler that translates from sequences of calculator operators into Clojure function definitions.

License and copyright

Copyright (c) KSM Technology Partners. All rights reserved.

The use and distribution terms for this software are covered by the Eclipse Public License 1.0 (http://opensource.org/licenses/eclipse-1.0.php) which can be found in the file epl-v10.html at the root of this distribution. By using this software in any fashion, you are agreeing to be bound by the terms of this license. You must not remove this notice, or any other, from this software.