Mastersign.Expressions

A parser and compiler for a small EXCEL like expression language inside your .NET applications.

Mastersign.Expression is a small DSL (domain specific language) – a little like the MS EXCEL formular language. Its purpose is to provide a simple expression language with a set of predefined functions for math and string manipulation. Expressions are parsed via a parser, based on the Sprache parser framework, and compiled via System.Linq.Expressions into a lambda delegate, and can therefore, used repeatedly with acceptable performance.

Eine deutsche Version der Projektbeschreibung befindet sich auf der Mastersign-Homepage (A german version of the project description can be found on the homepage of mastersign): https://www.mastersign.de/expressions

See the docs for more usage examples and reference documentation.

Installation from Nuget

dotnet add package Mastersign.Expressions

Features

Mastersign.Expression supports numeric, boolean and string literals, operators for numeric operations, string concatenation, logical combination and comparison. Grouping is done with parantheses. Function calls have a C-style-syntax. Functions, variables, constants, and parameters are provided via an evaluation context, which can be easily extended by the developer.

It comes with a set of predefined functions for math, string manipulation and regular expressions. For detailed description, see Packages.

The evaluation context can be configured to ignore the case of operator keywords, literal keywords, variables, parameters, and function names. The quote style for strings can be configured too.

Expression Examples

• 1 + 2
• pi * (100f + 32.0/a)
• "\tName: " & name
• "result = " & (sin(pi * 2.0 + x) / 10)

For a detailed description of the expression language syntax see Expression Syntax.

Simple Usage Scenario

using System;
using Mastersign.Expressions;

static class Program
{
    static void Main()
    {
        // create the evaluation context for the expression
        var context = new EvaluationContext();
        // set language options
        context.Options = LanguageOptions.Create(ignoreCase: true);
        // load the default packages with functions and constants (math, string, ...)
        context.LoadAllPackages();
        // add a custom variable
        context.SetVariable("x", 4);
        // add a custom function
        context.AddFunction<double, double>("neg", v => -v);
        // set parameter list
        context.SetParameters(new ParameterInfo("a", typeof(int)));
        // compile the expression into a lamda delegate
        var fun = context.CompileExpression<int, double>("SIN(PI * NEG(10 + x)) + a");
        // call the delegate and write the result to the console
        Console.WriteLine(fun(50));
    }
}

For more examples see Examples.

Screenshot of the Demo Application

Generation of a gray-scale bitmap with an expression:

Error reporting during parsing and compilation:

License

This project is published under the MIT license.

Copyright © by Tobias Kiertscher [email protected]