// 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>
/// Negates an <see cref="Expression"/>.
/// </summary>
public class Negative : PreUnaryOperator
{
#region /* CONSTANTS */
/// <summary>
/// The internal name of the operator.
/// </summary>
public const string InternalName = NamePrefix + "UnaryNegation";
#endregion
#region /* CONSTRUCTORS */
/// <summary>
/// Create a <see cref="Negative"/> operator.
/// </summary>
public Negative(Expression expression)
: base(expression)
{ }
#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="UnaryOperator"/>.
/// </summary>
public override string GetInternalName()
{
return InternalName;
}
#endregion
#region /* PARSING */
/// <summary>
/// The token used to parse the code object.
/// </summary>
public const string ParseToken = Subtract.ParseToken;
/// <summary>
/// The precedence of the operator.
/// </summary>
public const int Precedence = 200;
/// <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()
{
// Use a parse-priority of 100 (Subtract uses 0)
Parser.AddOperatorParsePoint(ParseToken, 100, Precedence, LeftAssociative, true, Parse);
}
/// <summary>
/// Parse a <see cref="Negative"/> operator.
/// </summary>
public static Negative Parse(Parser parser, CodeObject parent, ParseFlags flags)
{
return new Negative(parser, parent);
}
protected Negative(Parser parser, CodeObject parent)
: base(parser, parent, false)
{ }
/// <summary>
/// Get the precedence of the operator.
/// </summary>
public override int GetPrecedence()
{
return Precedence;
}
#endregion
#region /* RESOLVING */
/// <summary>
/// Evaluate the type of the <see cref="Expression"/>.
/// </summary>
/// <returns>The resulting <see cref="TypeRef"/> or <see cref="UnresolvedRef"/>.</returns>
public override TypeRefBase EvaluateType(bool withoutConstants)
{
// If we have a reference to an overloaded operator declaration, use its return type
if (_operatorRef is OperatorRef)
return ((OperatorRef)_operatorRef).GetReturnType();
// Determine the type of the expression
TypeRefBase typeRefBase = _expression.EvaluateType(withoutConstants);
if (typeRefBase is TypeRef)
{
// Handle a constant
if (typeRefBase.IsConst)
{
object result = EvaluateConstant(typeRefBase.GetConstantValue());
return (result != null ? new TypeRef(result) : typeRefBase);
}
// String, boolean, or enum operands aren't supported by default, but we'll just return the
// unchanged type instead of 'object'.
// Do unary numeric promotions
if (typeRefBase.IsSameRef(TypeRef.ShortRef) || typeRefBase.IsSameRef(TypeRef.UShortRef)
|| typeRefBase.IsSameRef(TypeRef.SByteRef) || typeRefBase.IsSameRef(TypeRef.ByteRef) || typeRefBase.IsSameRef(TypeRef.CharRef))
return TypeRef.IntRef;
if (typeRefBase.IsSameRef(TypeRef.UIntRef))
return TypeRef.LongRef;
}
// By default, the type is unchanged
return typeRefBase;
}
/// <summary>
/// Make a constant object negative.
/// Supported types are: string, bool, enum, decimal, double, float, ulong, long, uint, int, ushort, short, char, byte, sbyte.
/// </summary>
/// <returns>
/// The result, using the appropriate result type, including promoting smaller types to int. Returns null if the operation is invalid.
/// </returns>
protected override object EvaluateConstant(object constant)
{
// Null, string, boolean, or enum operands aren't supported
if (constant == null || constant is string || constant is bool || constant is EnumConstant)
return null; // The operation is invalid
// Do unary numeric promotions
if (constant is decimal)
return -(decimal)constant;
if (constant is double)
return -(double)constant;
if (constant is float)
return -(float)constant;
if (constant is ulong)
{
// Special case for long.MinValue
if ((ulong)constant == 9223372036854775808)
return -9223372036854775808;
return null; // The operation is invalid
}
if (constant is long)
return -(long)constant;
if (constant is uint)
{
// Special case for int.MinValue
if ((uint)constant == 2147483648)
return -2147483648;
return -Convert.ToInt64(constant);
}
if (constant is int)
return -(int)constant;
// All other cases (with smaller integral types) get promoted to ints
return -Convert.ToInt32(constant);
}
#endregion
}
}