FormalParameter.cs

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using System;
using System.Globalization;

namespace Mercury.Interpreting
{
//==<<  ParameterType  >>======================================================

    public enum ParameterType
    {
        IntegralConstant,
        RealConstant,
        StringConstant,
        BooleanConstant,
        Variable,
        ActionCall
    }

//=============================================================================
//  IFormalParameter
//=============================================================================

    public interface IFormalParameter
    {
        ParameterType Type { get; }
    }

//=============================================================================
//  ConstantParameter
//=============================================================================

    public class ConstantParameter : IFormalParameter, IEquatable<ConstantParameter>
    {
        //--[  Constructors  ]-------------------------------------------------

        public ConstantParameter(object value, ParameterType type)
        {
            if (value == null) throw new ArgumentNullException("value");

            Value = value;
            Type  = type;
        }

        //--[  Properties  ]---------------------------------------------------

        public object Value { get; protected set; }

        //--[  Methods  ]------------------------------------------------------


        public static ConstantParameter IntegralParameter(int value)
        { return new ConstantParameter(value, ParameterType.IntegralConstant); }

        public static ConstantParameter RealParameter(double value)
        { return new ConstantParameter(value, ParameterType.RealConstant); }

        public static ConstantParameter BooleanParameter(bool value)
        { return new ConstantParameter(value, ParameterType.BooleanConstant); }

        public static ConstantParameter StringParameter(string value)
        { return new ConstantParameter(value, ParameterType.StringConstant); }

        public static ConstantParameter AutoCreate(string value)
        {
            int ip; double dp; bool bp;

            var culture = CultureInfo.InvariantCulture;
            if      (   int.TryParse(value, NumberStyles.Integer, culture, out ip)) 
                return IntegralParameter(ip);
            else if (double.TryParse(value, NumberStyles.Float,   culture, out dp)) 
                return RealParameter(dp);
            else if (  bool.TryParse(value, out bp)) 
                return BooleanParameter(bp);
            else                                     
                return StringParameter(value);
        }

        //--[  Overriden methods  ]--------------------------------------------

        #region [  Object            ]

        public override bool Equals(object obj)
        {
            ConstantParameter cp = obj as ConstantParameter;
            return (cp == null) ? false : Equals(cp);
        }

        public override int GetHashCode()
        { return (((int) Type) + 1) * Value.GetHashCode(); }

        public override string ToString()
        { return Type == ParameterType.StringConstant ? "\"" + Value.ToString() + "\"" : Value.ToString(); }

        #endregion

        //--[  Interface implementation  ]-------------------------------------

        #region [  IFormalParameter  ]

        public ParameterType Type { get; protected set; }

        #endregion

        #region [  IEquatable        ]

        public bool Equals(ConstantParameter other)
        {
            return (other != null)
                && (Type  == other.Type)
                && (Value.Equals(other.Value));
        }

        #endregion

    }

//=============================================================================
//  VariableParameter
//=============================================================================

    public class VariableParameter : IFormalParameter, IEquatable<VariableParameter>
    {
        //--[  Constructors  ]-------------------------------------------------

        public VariableParameter(string name)
        {
            if (!Variable.IsValidName(name))
                throw new ArgumentException(string.Format("Invalid variable name '{0}'", name));

            Name = name;
            Type = ParameterType.Variable;
        }

        //--[  Properties  ]---------------------------------------------------

        public string Name { get; private set; }

        //--[  Overriden methods  ]--------------------------------------------

        #region [  Object            ]

        public override bool Equals(object obj)
        {
            VariableParameter vp = obj as VariableParameter;
            return vp == null ? false : Equals(vp);
        }

        public override int GetHashCode()
        { return Name.GetHashCode(); }

        public override string ToString()
        { return "#" + Name; }

        #endregion

        //--[  Interface implementation  ]-------------------------------------

        #region [  IFormalParameter  ]

        public ParameterType Type { get; private set; }

        #endregion

        #region [  IEquatable        ]

        public bool Equals(VariableParameter other)
        { return (other != null) && (Name.Equals(other.Name)); }

        #endregion

    }
}