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ExpressionCalculator

A simple expression calculator for the 4 operations and exponentiation.

  • Parses to a tree using a recursive descent parser (so it is human readable).
  • The tree can then be directly evaluated using a recursive evaluation.
  • Also includes a stack-based, step-wise evaluator.

Includes a both a traditional factor/term grammar parser and evaluator and an associative grammar parser and evaluator that separates out sums from differences and products from quotients. The associative grammar is designed to separate out operations that are subject to the associative and commutative properties with the notion that the parse tree can then be more easily queried or manipulated using those mathematical properties. For example the AssocativeTreeHelper.generateCommutedExpressions() method can generate a set of equivalent expressions by applying the commutative property. That method is used by AssociativeTreeHelper.areExpressionsEquivalent() to test is two expressions are equivalent based on the commutative property.

Build using command line

  • install a Java 8 compiler and runtime and add it to your path
  • install maven package and build system and add it to your path
  • git clone this repo
  • run tests with mave from root of project folder
$ mvn test
  • build with maven from root of project folder
$ mvn package
  • to run from root of project folder
$ java -jar target/expression-calculator-0.9-SNAPSHOT.jar "1 + 2 / 3 * (4 + 5)"
  1 + 2 / 3 * (4 + 5)
  1 + 2 / 3 * (4 + 5) = 7.0

IntelliJ

  • install IntelliJ IDE
  • git clone this repo
  • start IntelliJ
  • if startup window opens, choose "Open or Import"
  • if start window does not open, from file menu choose "new/project from existing sources"
  • Navigate to project root folder and choose the pom.xml file.
  • IntelliJ will create the project if it does not already exist or open the existing project.
  • to run tests in IntelliJ, choose LifeCycle/test in the Maven panel
  • to build in IntelliJ, choose LifeCycle/package in the Maven panel