Binary Expression Tree

A binary expression tree library for Java.

Design & Features

• Infix notation
• Supported types: String, int, long, float, double, BigInteger, BigDecimal
• Basic math operators: +, -, /, *, %, ** (exponentiation)
• Basic boolean operators: &&, ||, =, !=, <, <=, >, >=
• Unary operators: -, !
• Expressions are built by chaining method calls instead of passing a string
• Nested (i.e. parenthesized) expressions
• Variables are mutable objects that can change the result of the next evaluation
• User-definable functions based on operator and operands' type
• Order of operations for binary operators can be reordered
• Left-to-right evaluation
• Short-circuit evaluation
• Expression parser uses the same Expression API to build an expression
• Expression printer outputs strings that can be parsed back

Installation

Gradle

dependencies {
	api 'com.javalbert:binary-expression-tree:1.0.0'
}

or Maven

<dependency>
	<groupId>com.javalbert</groupId>
	<artifactId>binary-expression-tree</artifactId>
	<version>1.0.0</version>
</dependency>

Basic Usage

Build expression, create tree, and evaluate:

// -2 * (3 + 4)
Expression expr = new Expression()
.negate().val(2).times()
.expr(new Expression()
	.val(3).plus().val(4));

Node node = new ExpressionTreeCreator(expr).create();

// -14
Object result = new ExpressionEvaluator().eval(node);

Variables

Variable<Integer> x = new IntVariable("x", 3);
// x ** 2
Expression expr = new Expression().val(x).powerOf().val(2);
// 9
Object result = new ExpressionEvaluator().eval(expr);

Parse expression from string:

Expression expr = new ExpressionParser().parse("1 < 2 && 3 < 4");

Print expression:

// 1 < 2 && 3 < 4
String exprString = new ExpressionPrinter().print(expr);