// The simples way to create a formula parser is the static method 'Create'. 
var parser = FormulaParser.Create();
    
// Parsing a simple mathematical formula
var result1 = parser.Evaluate("1+1").Value; // result1 = 2.0
    
// Usage of variables
var variables = new Dictionary<string, double> { ["x"] = 2.0 };
var result2 = parser.Evaluate("1+x", variables).Value; // result2 = 3.0
    
// Usage of functions
var result3 = parser.Evaluate("1+min(3,4)").Value; // result3 = 4.0
    
// Handle errors
var parsingResult = parser.Evaluate("2*?");
if (!parsingResult.Success)
{
    Console.WriteLine(parsingResult.Error); // "column 2: token recognition error at: '?'"
}

var parser = FormulaParser.Create();
var variables = new Dictionary<string, double> { ["x"] = 2.0 };

// Parsing a simple mathematical formula
var node1 = parser.Parse("1+x", variables).Value;
// |FormulaNode("1+x")
// |- Child: BinaryOperatorNode(+)
//           |- LeftNode:  NumericNode(1.0)
//           |- RightNode: VariableNode("x")
var result1 = parser.Evaluate(node1, variables).Value; // result = 3.0


var node2 = parser.Parse("pi * sqrt(3*x)", variables).Value;
// |FormulaNode("pi * sqrt(3*x)")
// |- Child: BinaryOperatorNode(*)
//           |- LeftNode:  ConstantNode("pi")
//           |- RightNode: FunctionNode("sqrt")
//                         |- Parameters: [BinaryOperationNode(*)]
//                                         |- LeftNode:  Numeric(3.0)
//                                         |- RightNode: VariableNode("x")                       
var result2 = parser.Evaluate(node2, variables).Value; // result = 7.695...

var parser = FormulaParser
    .CreateBuilder()
    .ConfigureConstats(constants =>
    {
        // constants.RemoveAll()    for removing all default constants
        // constants.Remove("pi")   for removing constants by name
            
        constants.Add("h", 6.62607015e-34);
    })
    .ConfigureFunctions(functions =>
    {
        // functions.RemoveAll()    for removing all default functions
        // functions.Remove("sum")  for removing function by name

        // define functions with certain number of parameters (1-5 parameters are supported)
        functions.Add("celsiusToFarenheit", celsius => celsius * 1.8 + 32);
        functions.Add("fahrenheitToCelsius", fahrenheit => (fahrenheit - 32) * 5 / 9);
        functions.Add("p1_plus_p2_plus_p3", (p1, p2, p3) => p1 + p2 + p3);
        
        // define function with 2 to n number of parameters (typeof(nums) = double[])
        functions.Add("product", nums => nums.Aggregate((p1, p2) => p1 * p2));
    }).Build();

var poolTemperatureInCelsius = parser.Evaluate("celsiusToFarenheit(fahrenheitToCelsius(30))").Value; // poolTemperatureInCelsius = 30
var result2 = parser.Evaluate("product(2, 2, 2, 2, 2, 2)").Value;    // result2 = 2^6 = 128
var result3 = parser.Evaluate("p1_plus_p2_plus_p3(1, 2, 3)").Value;     // result3 = 6

string error1 = parser.Evaluate("celsiusToFarenheit(1, 2)").Error;      // column 0: There is no function 'celsiusToFarenheit' that takes 2 argument(s).
    string error2 = parser.Evaluate("product()").Error;                     // column 0: There is no function 'product' that takes 0 argument(s).
string error3 = parser.Evaluate("p1_plus_p2_plus_p3(1, 2)").Error;      // column 0: There is no function 'p1_plus_p2_plus_p3' that takes 2 argument(s).