Intro

NCalc is a mathematical expression evaluator in .NET. NCalc can parse any expression and evaluate the result, including static or dynamic parameters and custom functions.

Project Description

NCalc is a mathematical expression evaluator in .NET. NCalc can parse any expression and evaluate the result, including static or dynamic parameters and custom functions.

For additional information on the technique we used to create this framework please read this article: http://www.codeproject.com/KB/recipes/sota_expression_evaluator.aspx.

Table of Contents

• Operators: Available standard operators and structures.
• Values: Authorized values like types and functions.
• Functions: List of already implemented functions.
• Parameters: How to use parameters expressions.
• Handling Errors: How to handle errors.
• Case Sensitivity: Options in how to handle case sensitivity.
• Overflow Handling: How to handle overflow with binary arithmetic operations
• Async Support: How and when to use async.
• Caching: How caching works.
• Improve performance: How to use compilation of expressions to CLR lambdas.
• Dependency Injection: Bring expressions to the next level with dependency injection.
• Benchmarks: Check some numbers about the speed of some NCalc components.

Expression

This is the main class of NCalc. The method Evaluate() returns the actual value of its string representation.

Example:

  var expression = new Expression("2 * 3");
  object result = expression.Evaluate();
  
  Console.WriteLine(result);

This example above first creates an instance of Expression using a valued constructor. This constructor takes a string as parameter. Then the method Evaluate() is called to parse the string, and returns the actual value represented by the string.

To create expressions you can combine several Operators and Values.

Functionalities

Simple Expressions

var expression = new Expression("2 + 3 * 5");
Debug.Assert(17 == expression.Evaluate());

.NET Data Types

Debug.Assert(123456 == new Expression("123456").Evaluate()); // integers
Debug.Assert(new DateTime(2001, 01, 01) == new Expression("#01/01/2001#").Evaluate()); // datetime
Debug.Assert(123.456 == new Expression("123.456").Evaluate()); // floating point numbers
Debug.Assert(true == new Expression("true").Evaluate()); // booleans
Debug.Assert("azerty" == new Expression("'azerty'").Evaluate()); // strings

Mathematical functional from System.Math**

Debug.Assert(0 == new Expression("Sin(0)").Evaluate());
Debug.Assert(2 == new Expression("Sqrt(4)").Evaluate());
Debug.Assert(0 == new Expression("Tan(0)").Evaluate());

Custom Functions

var expression = new Expression("SecretOperation(3, 6)");
expression.EvaluateFunction += delegate(string name, FunctionArgs args)
    {
        if (name == "SecretOperation")
            args.Result = (int)args.Parameters[0].Evaluate() + (int)args.Parameters[1].Evaluate();
    };

Debug.Assert(9 == expression.Evaluate());

Unicode Characters

Debug.Assert("経済協力開発機構" == new Expression("'経済協力開発機構'").Evaluate());
Debug.Assert("Hello" == new Expression(@"'\u0048\u0065\u006C\u006C\u006F'").Evaluate());
Debug.Assert("だ" == new Expression(@"'\u3060'").Evaluate());
Debug.Assert("\u0100" == new Expression(@"'\u0100'").Evaluate());

Parameters - Static and Dynamic

var expression = new Expression("Round(Pow([Pi], 2) + Pow([Pi2], 2) + [X], 2)");

expression.Parameters["Pi2"] = new Expression("Pi * [Pi]");
expression.Parameters["X"] = 10;

expression.EvaluateParameter += delegate(string name, ParameterArgs args)
  {
    if (name == "Pi")
        args.Result = 3.14;
  };

Debug.Assert(117.07 == expression.Evaluate());

Lambda Expressions

var expression = new Expression("1 + 2");
Func<int> function = expression.ToLambda<int>();
Debug.Assert(function()); //3