schemy/src/schemy/CommonTypes.cs

// Copyright (c) Microsoft Corporation. All rights reserved.
// Licensed under the MIT License.

namespace Schemy
{
    using System;
    using System.Collections.Generic;

    public class None
    {
        public static readonly None Instance = new None();
    }

    class AssertionFailedError : Exception
    {
        public AssertionFailedError(string msg) : base(msg)
        {
        }
    }

    class SyntaxError : Exception
    {
        public SyntaxError(string msg) : base(msg)
        {
        }
    }

    /// <summary>
    /// Poor man's discreminated union
    /// </summary>
    public class Union<T1, T2>
    {
        private readonly object data;
        public Union(T1 data)
        {
            this.data = data;
        }

        public Union(T2 data)
        {
            this.data = data;
        }

        public TResult Use<TResult>(Func<T1, TResult> func1, Func<T2, TResult> func2)
        {
            if (this.data is T1)
            {
                return func1((T1)this.data);
            }
            else
            {
                return func2((T2)this.data);
            }
        }
    }
}