📜 Introduction

This is a simple expression evaluator that can evaluate expressions with created and provided operators, pre-processors, post-processors.

Provided text in expressions must be surrounded by double quotes to keep the text as it is, otherwise whitespace is trimmed and the result may not be as expected.

fun main() {
    // Creating an instance that wraps around a few parameters
    val expressions = Expressions()

    check(expressions.evaluate("true || false")) // true
    check(!expressions.evaluate("true && false")) // false
    check(expressions.evaluate("true && false || true")) // true
    check(expressions.evaluate("\"hot mom in town\" contains \"mom\"")) // true

    // Set parameters to use in further evaluations
    expressions.setParameters(
        mapOf(
            "dadSaid" to "Great Job Son",
            "age" to 18
        )
    )

    // \"dadSaid\" is replaced with \"Great Job Son\" when evaluating
    check(expressions.evaluate("dadSaid == \"Great Job Son\"")) // true
    check(!expressions.evaluate("dadSaid == Great Job Son")) // false, because of whitespace trimming
    check(expressions.evaluate("age >= 18")) // true

    expressions.setParameter("age" to 17)

    check(!expressions.evaluate("age >= 18")) // false
}

🟰 Case-insensitive comparison

In case it is wanted to compare strings in case-insensitive way with IgnoreCasePreprocessor, then ReplacementsPreprocessor should be provided with string parameters to replace strings beforehand. This may or may not be reworked in the future to support case-insensitive comparison at the parameters' resolution.

😎 Extendable

You can add ExpressionPreprocessor, ExpressionOperator and ExpressionPostprocessor to extend this simple expression evaluator even further.