AlphaX.FormulaEngine 2.2.0

AlphaX.FormulaEngine

A strong and fast library to parse and evaluate formulas. It also supports custom formulas. This library is built using 'AlphaX.Parserz' library.

GitHub Repo : https://github.com/kartikdeepsagar/AlphaX.FormulaEngine

Feedback is very much appreciated : https://forms.gle/dfv8E8zpC2qPJS7i7

Using AlphaXFormulaEngine

For evaluating formulas using AlphaXFormulaEngine, you can simply initialize the engine and start using its Evaluate method:

AlphaX.FormulaEngine.AlphaXFormulaEngine engine = new AlphaX.FormulaEngine.AlphaXFormulaEngine();
AlphaX.FormulaEngine.IEvaluationResult result = engine.Evaluate("SUM([1,2,12.3,5.9099])");
Console.WriteLine(result.Value); // 21.2099

AlphaXFormulaEngine comes with a limited number (not many) of inbuilt formulas i.e.

Arithmetic Formulas

• SUM - Returns sum of provided values. For example: SUM([1,2,4]) // 7
• AVERAGE - Returns average of provided values. For example: AVERAGE([3,2,4]) // 3

String Formulas

• LOWER - Returns lower cased string. For example: LOWER("TESTSTRING") // teststring
• UPPER - Returns upper cased string. For example: UPPER("teststring") // TESTSTRING
• TEXTSPLIT - Returns splitted string using a seperator. For example: TEXTSPLIT(".", "John.Doe") // John Doe
• CONCAT - Joins multiple strings into one string: For example: CONCAT("Test","String","1") // TestString1
• LENGTH - Gets the length of a string. For example: LENGTH("AlphaX") // 6
• CONTAINS - Checks if a string contains another string. For example: CONTAINS("AlphaX", "pha") // true
• STARTSWITH - Checks if a string starts with the provided string. Accepts third (optional) parameter as boolean to match case. Default = false. For example: STARTSWITH("AlphaX", "Al", true) // true
• ENDSWITH - Checks if a string starts with the provided string. Accepts third (optional) parameter as boolean to match case. Default = false. For example: ENDSWITH("AlphaX", "Al") // false

DateTime Formulas

• TODAY - Returns system date. For example: TODAY() // 28-04-2023
• NOW - Returns system date time // 28-04-2023 10:52:53 PM

Logical Formulas

• EQUALS - Checks if two values/expressions are equal. For example: EQUALS(true, 1 > 3) // false
• GREATERTHAN - Checks if one value/expressions is greater than other. For example: GREATERTHAN(5,2) // true
• GREATERTHANEQUALS - Checks if one value/expressions is greater than or equal to other. For example: GREATERTHANEQUALS(5,2) // true
• LESSTHAN - Checks if one value/expressions is less than other. For example: LESSTHAN(5,2) // false
• LESSTHANEQUALS - Checks if one value/expressions is less than or equal to other. For example: LESSTHANEQUALS(5,2) // false
• NOT - Inverse a boolean value/expression. For example: NOT(1 == 1) // false
• AND - Performs AND (&&) operation between 2 boolean values/expressions. For example: AND(true, 1 != 1) // false
• OR - Performs OR (||) operation between 2 boolean values/expressions. For example: OR(true, 1 != 1) // true

Array Formulas

• ARRAYCONTAINS - Checks if array contains a value. For example: ARRAYCONTAINS([1,2,3], 2) // true
• ARRAYINCLUDES - Checks if array includes all values. For example: ARRAYINCLUDES([1,2,3,4], [3,4]) // true

Note : More formulas will be added in future updates.

Creating a Custom Formula

This is one of the best feature of AlphaXFormulaEngine. It provides you enough flexibility to write your own formula and easily integrate it with the engine.

1. Create a new MyFormula class which inherits from AlphaX.FormulaEngine.Formula class

public class MyFormula : AlphaX.FormulaEngine.Formula
{
        public MyFormula() : base("MyFormula")
        {
        }

        public override object Evaluate(params object[] args)
        {
            throw new NotImplementedException();
        }

        protected override FormulaInfo GetFormulaInfo()
        {
            throw new NotImplementedException();
        }
}

In the above code, the base() call accepts the name of the formula to be used in formula string.

2. Let's just say our formula will return a number raised to a power. For example. 2^2 = 4. So, we'll start by writing the code in the above evaluate method as follows:

public override object Evaluate(params object[] args)
{
            double result = 0;
            if (args.Length != 2)
            {
                double number = (double)args[0];
                double power = (double)args[1];
                result = Math.Pow(number, power);
            }
            return result;
}

3. We also need to provide some additional metadata for our formula using the GetFormulaInfo method as follows:

protected override FormulaInfo GetFormulaInfo()
{
    var info = new FormulaInfo();
    info.AddArgument(new DoubleArgument("number", true));
    info.AddArgument(new DoubleArgument("number", true));
    return info;
}

The above code defines that our formula:

• Will have min/max 2 arguments.
• First argument is a number of type double, It is required and will be present at 0 index in formula arguments.
• Second argument is a number of type double, It is required and will be present at 1 index in formula arguments.

4. Now our formula is ready and the only thing left is to integrate it with the engine by using AlphaXFormulaEngine's AddFormula method as follows:

AlphaX.FormulaEngine.AlphaXFormulaEngine engine = new AlphaX.FormulaEngine.AlphaXFormulaEngine();
engine.FormulaStore.Add(new MyFormula());
AlphaX.FormulaEngine.IEvaluationResult result = engine.Evaluate("MyFormula(4,3)");
Console.WriteLine(result.Value); // 64

Customizing Engine Settings

AlphaXFormulaEngine allows you to customize the formula string format. By, default the formula format is :

FormulaName(argument1, argument2, argument3......)

However, you can customize this as per your needs. For example, you can change it to:

FormulaName[argument1 | argument 2 | argument 3....]

Doing this is a piece of cake using engine settings as follows:

AlphaX.FormulaEngine.AlphaXFormulaEngine engine = new AlphaX.FormulaEngine.AlphaXFormulaEngine();
engine.Settings.ArgumentsSeparatorSymbol = "|";
engine.Settings.OpenBracketSymbol = "[";
engine.Settings.CloseBracketSymbol = "]";
engine.Settings.Save();

engine.AddFormula(new MyFormula());
AlphaX.FormulaEngine.IEvaluationResult result = engine.Evaluate("MyFormula[4|3]");
Console.WriteLine(result.Value); // 64

Nested Formulas

To make your life easy, we have also added support for nested formulas. So, you can use a formula as a formula argument for another formula as follows:

AlphaX.FormulaEngine.IEvaluationResult result = engine.Evaluate("MyFormula(4, MyFormula(2,2))");
Console.WriteLine(result.Value); // 256

That's all of it 😃