How to write a Parser in C#? [closed]

Answer 1

Sprache is a powerful yet lightweight framework for writing parsers in .NET. There is also a Sprache NuGet package. To give you an idea of the framework here is one of the samples that can parse a simple arithmetic expression into an .NET expression tree. Pretty amazing I would say.

using System;
using System.Linq.Expressions;
using Sprache;

namespace LinqyCalculator
{
    static class ExpressionParser
    {
        public static Expression> ParseExpression(string text)
        {
            return Lambda.Parse(text);
        }

        static Parser Operator(string op, ExpressionType opType)
        {
            return Parse.String(op).Token().Return(opType);
        }

        static readonly Parser Add = Operator("+", ExpressionType.AddChecked);
        static readonly Parser Subtract = Operator("-", ExpressionType.SubtractChecked);
        static readonly Parser Multiply = Operator("*", ExpressionType.MultiplyChecked);
        static readonly Parser Divide = Operator("/", ExpressionType.Divide);

        static readonly Parser Constant =
            (from d in Parse.Decimal.Token()
             select (Expression)Expression.Constant(decimal.Parse(d))).Named("number");

        static readonly Parser Factor =
            ((from lparen in Parse.Char('(')
              from expr in Parse.Ref(() => Expr)
              from rparen in Parse.Char(')')
              select expr).Named("expression")
             .XOr(Constant)).Token();

        static readonly Parser Term = Parse.ChainOperator(Multiply.Or(Divide), Factor, Expression.MakeBinary);

        static readonly Parser Expr = Parse.ChainOperator(Add.Or(Subtract), Term, Expression.MakeBinary);

        static readonly Parser>> Lambda =
            Expr.End().Select(body => Expression.Lambda>(body));
    }
}