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Resolving Symbolic References in a CodeDOM (Part 7)

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2 Dec 2012CDDL12 min read 19.3K   508   14  
Resolving symbolic references in a CodeDOM.
// The Nova Project by Ken Beckett.
// Copyright (C) 2007-2012 Inevitable Software, all rights reserved.
// Released under the Common Development and Distribution License, CDDL-1.0: http://opensource.org/licenses/cddl1.php

using System;

using Nova.Parsing;

namespace Nova.CodeDOM
{
    /// <summary>
    /// The GreaterThanEqual operator checks if the left Expression is greater than or equal to the right Expression.
    /// </summary>
    public class GreaterThanEqual : RelationalOperator
    {
        #region /* CONSTANTS */

        /// <summary>
        /// The internal name of the operator.
        /// </summary>
        public const string InternalName = NamePrefix + "GreaterThanOrEqual";

        #endregion

        #region /* CONSTRUCTORS */

        /// <summary>
        /// Create a <see cref="GreaterThanEqual"/> operator.
        /// </summary>
        public GreaterThanEqual(Expression left, Expression right)
            : base(left, right)
        { }

        #endregion

        #region /* PROPERTIES */

        /// <summary>
        /// The symbol associated with the operator.
        /// </summary>
        public override string Symbol
        {
            get { return ParseToken; }
        }

        #endregion

        #region /* METHODS */

        /// <summary>
        /// The internal name of the <see cref="BinaryOperator"/>.
        /// </summary>
        public override string GetInternalName()
        {
            return InternalName;
        }

        #endregion

        #region /* PARSING */

        /// <summary>
        /// The token used to parse the code object.
        /// </summary>
        public const string ParseToken = ">=";

        /// <summary>
        /// The precedence of the operator.
        /// </summary>
        public const int Precedence = 330;

        /// <summary>
        /// True if the operator is left-associative, or false if it's right-associative.
        /// </summary>
        public const bool LeftAssociative = true;

        internal static new void AddParsePoints()
        {
            Parser.AddOperatorParsePoint(ParseToken, Precedence, LeftAssociative, false, Parse);
        }

        /// <summary>
        /// Parse a <see cref="GreaterThanEqual"/> operator.
        /// </summary>
        public static GreaterThanEqual Parse(Parser parser, CodeObject parent, ParseFlags flags)
        {
            return new GreaterThanEqual(parser, parent);
        }

        protected GreaterThanEqual(Parser parser, CodeObject parent)
            : base(parser, parent)
        { }

        /// <summary>
        /// Get the precedence of the operator.
        /// </summary>
        public override int GetPrecedence()
        {
            return Precedence;
        }

        #endregion

        #region /* RESOLVING */

        /// <summary>
        /// Compare if the first constant object is greater than the second.
        /// Supported types are: string, bool, enum, decimal, double, float, ulong, long, uint, int, ushort, short, char, byte, sbyte.
        /// </summary>
        protected override object EvaluateConstants(object leftConstant, object rightConstant)
        {
            // Check for null, string, or bool
            if (leftConstant == null || rightConstant == null || leftConstant is string || rightConstant is string
                || leftConstant is bool || rightConstant is bool)
                return null;  // The operation is invalid

            // Check for enum types
            if (leftConstant is EnumConstant || rightConstant is EnumConstant)
            {
                if (leftConstant is EnumConstant && rightConstant is EnumConstant)
                {
                    EnumConstant leftEnum = (EnumConstant)leftConstant;
                    EnumConstant rightEnum = (EnumConstant)rightConstant;
                    if (leftEnum.EnumTypeRef.IsSameRef(rightEnum.EnumTypeRef))
                        return EvaluateConstants(leftEnum.ConstantValue, rightEnum.ConstantValue);
                }
                return null;  // The operation is invalid
            }

            // Do binary numeric promotions
            if (leftConstant is decimal)
            {
                if (!(rightConstant is float || rightConstant is double))
                    return (decimal)leftConstant >= Convert.ToDecimal(rightConstant);
                return null;  // The operation is invalid
            }
            if (rightConstant is decimal)
            {
                if (!(leftConstant is float || leftConstant is double))
                    return Convert.ToDecimal(leftConstant) >= (decimal)rightConstant;
                return null;  // The operation is invalid
            }
            if (leftConstant is double)
                return (double)leftConstant >= Convert.ToDouble(rightConstant);
            if (rightConstant is double)
                return Convert.ToDouble(leftConstant) >= (double)rightConstant;
            if (leftConstant is float)
                return (float)leftConstant >= Convert.ToSingle(rightConstant);
            if (rightConstant is float)
                return Convert.ToSingle(leftConstant) >= (float)rightConstant;
            if (leftConstant is ulong)
            {
                if ((rightConstant is sbyte && (sbyte)rightConstant < 0) || (rightConstant is short && (short)rightConstant < 0)
                    || (rightConstant is int && (int)rightConstant < 0) || (rightConstant is long && (long)rightConstant < 0))
                    return null;  // The operation is invalid
                return (ulong)leftConstant >= Convert.ToUInt64(rightConstant);
            }
            if (rightConstant is ulong)
            {
                if ((leftConstant is sbyte && (sbyte)leftConstant < 0) || (leftConstant is short && (short)leftConstant < 0)
                    || (leftConstant is int && (int)leftConstant < 0) || (leftConstant is long && (long)leftConstant < 0))
                    return null;  // The operation is invalid
                return Convert.ToUInt64(leftConstant) >= (ulong)rightConstant;
            }
            if (leftConstant is long)
                return (long)leftConstant >= Convert.ToInt64(rightConstant);
            if (rightConstant is long)
                return Convert.ToInt64(leftConstant) >= (long)rightConstant;
            if (leftConstant is uint)
            {
                if ((rightConstant is sbyte && (sbyte)rightConstant < 0) || (rightConstant is short && (short)rightConstant < 0)
                    || (rightConstant is int && (int)rightConstant < 0))
                    return Convert.ToInt64(leftConstant) >= Convert.ToInt64(rightConstant);
                return (uint)leftConstant >= Convert.ToUInt32(rightConstant);
            }
            if (rightConstant is uint)
            {
                if ((leftConstant is sbyte && (sbyte)leftConstant < 0) || (leftConstant is short && (short)leftConstant < 0)
                    || (leftConstant is int && (int)leftConstant < 0))
                    return Convert.ToInt64(leftConstant) >= Convert.ToInt64(rightConstant);
                return Convert.ToUInt32(leftConstant) >= (uint)rightConstant;
            }
            // All other cases (with smaller integral types) get promoted to ints
            return Convert.ToInt32(leftConstant) >= Convert.ToInt32(rightConstant);
        }

        #endregion
    }
}

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This article, along with any associated source code and files, is licensed under The Common Development and Distribution License (CDDL)


Written By
Software Developer (Senior)
United States United States
I've been writing software since the late 70's, currently focusing mainly on C#.NET. I also like to travel around the world, and I own a Chocolate Factory (sadly, none of my employees are oompa loompas).

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