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This library provides easy to use extensible expression evaluator based onLinqyCalculator sample.The evaluator supports arithmetic operations, custom functions and parameters. It takes stringrepresentation of an expression and converts it to a structured LINQ expression instancewhich can easily be compiled to an executable delegate. In contrast with interpreted expressionevaluators such as NCalc, compiled expressions perform just as fast as native C# methods.

varcalc=newSprache.Calc.XtensibleCalculator();// using expressionsvarexpr=calc.ParseExpression("Sin(y/x)", x=>2, y=>System.Math.PI);varfunc=expr.Compile();Console.WriteLine("Result = {0}",func());// custom functionscalc.RegisterFunction("Mul",(a,b,c)=>a*b*c);expr=calc.ParseExpression("2 ^ Mul(PI, a, b)", a=>2, b=>10);Console.WriteLine("Result = {0}",expr.Compile()());// end-user's functionscalc.RegisterFunction("Add","a + b","a","b");expr=calc.ParseExpression("Add(353, 181)");Console.WriteLine("Result = {0}",expr.Compile()());

To use expression evaluator in your projects, installSprache.Calc NuGet packageby running the following command in the Package Manager Console:

PM> Install-Package Sprache.Calc

Sprache.Calc library serves as a demonstration of grammar inheritance technique with Sprache toolkit.An article describing Sprache.Calc implementation details is currently available in English and Russian:

• Sprache.Calc: building yet another expression evaluator
• Наследование грамматик в Sprache на примере калькулятора выражений.

TL;DR:

• Declare parsers as virtual properties instead of static fields
• Decompose the grammar into small and reusable rules
• Write unit tests for every single atomic parser
• Use "protected internal" access modifier to enable unit testing
• Unit tests must be organized in the same hierarchy as parser classes