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ExprK

A simple mathematical expression evaluator for Kotlin and Java, written in Kotlin.

Features:

  • Uses BigDecimal for calculations and results
  • Allows you to define variables using values or expressions
  • Variable definition expressions can reference previously defined variables
  • Configurable precision and rounding mode
  • Functions and the ability to define new ones

Supported operators

Arithmetic operators

Name Operator
Plus +
Minus -
Multiply *
Divide /
Modulus %
Exponent ^

Logical operators

Name Operator
And &&
Or ||

Pre-defined variables

Variable Value
pi 3.141592653589793
e 2.718281828459045

Pre-defined functions

Function Description
abs(expression) Returns the absolute value of the expression
sum(expression, ...) Returns the sum of all arguments
floor(expression) Rounds the value of the expression down to the nearest integer
ceil(expression) Rounds the value of the expression up to the nearest integer
round(expression) Rounds the value of the expression to the nearest integer in the direction decided by the configured rounding mode
min(expression, ...) Returns the value of the smallest argument
max(expression, ...) Returns the value of the largest argument
if(condition, trueValue, falseValue) Returns trueValue if condition is true(condition != 0), otherwise it returns falseValue

Examples:

val result = Expressions()
    .eval("(5+5)*10") // returns 100

You can define variables with the define method.

val result = Expressions()
    .define("x", 5)
    .eval("x*10") // returns 50

The define method returns the expression instance to allow chaining definition method calls together.

val result = Expressions()
    .define("x", 5)
    .define("y", "5*2")
    .eval("x*y") // returns 50

Variable definition expressions can reference previously defined variables.

val result = Expressions()
    .define("x", 5)
    .define("y", "x^2")
    .eval("y*x") // returns 125

You can add new functions with the addFunction method.

val result = Expressions()
    .addFunction("min") { arguments ->
        if (arguments.isEmpty()) throw ExpressionException(
                "min requires at least one argument")

        arguments.min()!!
    }
    .eval("min(4, 8, 16)") // returns 4

You can set the precision and rounding mode with setPrecision and setRoundingMode.

val result = Expressions()
    .setPrecision(128)
    .setRoundingMode(RoundingMode.UP)
    .eval("222^3/5.5")