NCalc

A clone of NCalc from http://ncalc.codeplex.com/ with the following changes:

• added support for CoreCLR (.NET Standard 1.3+)
• embedded portable version of Antlr (no extra library/dependency required)
• added compilation of expressions to actual CLR lambdas

Installation

Simply install the package via NuGet

PM> Install-Package CoreCLR-NCalc

Creating Lambdas

Simple Expressions

var expr = new Expression("1 + 2");
Func<int> f = expr.ToLambda<int>();
Console.WriteLine(f()); // will print 3

Expressions with Functions and Parameters

class ExpressionContext
{
  public int Param1 { get; set; }
  public string Param2 { get; set; }
  
  public int Foo(int a, int b)
  {
    return a + b;
  }
}

var expr = new Expression("Foo([Param1], 2) = 4 && [Param2] = 'test'");
Func<ExpressionContext, bool> f = expr.ToLambda<ExpressionContext, bool>();

var context = new ExpressionContext { Param1 = 2, Param2 = "test" };
Console.WriteLine(f(context)); // will print True

Performance Comparison

The measurements were done during CI runs on AppVeyor and fluctuate a lot in between runs, but the speedup is consistently in the thousands of percent range. The speedup measured on actual hardware was even higher (between 10,000% and 35,000%).

Formula	Description	Expression Evaluations / sec	Lambda Evaluations / sec	Speedup
(4 * 12 / 7) + ((9 * 2) % 8)	Simple Arithmetics	474,247.87	32,691,490.41	6,793.33%
5 * 2 = 2 * 5 && (1 / 3.0) * 3 = 1	Simple Arithmetics	276,226.31	93,222,709.05	33,648.67%
[Param1] * 7 + [Param2]	Constant Values	707,493.27	21,766,101.47	2,976.51%
[Param1] * 7 + [Param2]	Dynamic Values	582,832.10	21,400,445.13	3,571.80%
Foo([Param1] * 7, [Param2])	Dynamic Values and Function Call	594,259.69	17,209,334.34	2,795.93%