// 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>
/// Subtracts one <see cref="Expression"/> from another.
/// </summary>
public class Subtract : BinaryArithmeticOperator
{
#region /* CONSTANTS */
/// <summary>
/// The internal name of the operator.
/// </summary>
public const string InternalName = NamePrefix + "Subtraction";
#endregion
#region /* CONSTRUCTORS */
/// <summary>
/// Create a <see cref="Subtract"/> operator.
/// </summary>
public Subtract(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 = 310;
/// <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="Subtract"/> operator.
/// </summary>
public static Subtract Parse(Parser parser, CodeObject parent, ParseFlags flags)
{
// Verify that we have a left expression before proceeding, otherwise abort
// (this is to give the Negative operator a chance at parsing it)
if (parser.HasUnusedExpression)
return new Subtract(parser, parent);
return null;
}
protected Subtract(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>
/// 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 types of both sides
TypeRefBase leftTypeRefBase = (_left != null ? _left.EvaluateType(withoutConstants) : null);
TypeRefBase rightTypeRefBase = (_right != null ? _right.EvaluateType(withoutConstants) : null);
if (leftTypeRefBase is TypeRef && rightTypeRefBase is TypeRef)
{
TypeRef leftTypeRef = (TypeRef)leftTypeRefBase;
TypeRef rightTypeRef = (TypeRef)rightTypeRefBase;
// Handle constants
if (!withoutConstants && leftTypeRef.IsConst && rightTypeRef.IsConst)
{
object result = EvaluateConstants(leftTypeRef.GetConstantValue(), rightTypeRef.GetConstantValue());
return (result != null ? new TypeRef(result) : TypeRef.ObjectRef);
}
// String or boolean operands aren't supported
if (leftTypeRef.IsSameRef(TypeRef.StringRef) || rightTypeRef.IsSameRef(TypeRef.StringRef)
|| leftTypeRef.IsSameRef(TypeRef.BoolRef) || rightTypeRef.IsSameRef(TypeRef.BoolRef))
return null;
// Enumeration subtraction: If both sides are of the same enum type, then the result is
// the underlying type of the enum. If the left side is an enum and right is of the enums
// underlying type (or is implicitly convertible to it), then the result is the enum type.
if (leftTypeRef.IsEnum)
{
// U -(E, E):
if (rightTypeRef.IsEnum)
return (leftTypeRef.IsSameRef(rightTypeRef) ? leftTypeRef.GetUnderlyingTypeOfEnum() : TypeRef.ObjectRef);
// E -(E, U):
return (rightTypeRef.IsImplicitlyConvertibleTo(leftTypeRef.GetUnderlyingTypeOfEnum()) ? leftTypeRef : TypeRef.ObjectRef);
}
}
// By default, determine a common type (using implicit conversions) that can handle the
// result of the operation.
return TypeRef.GetCommonType(leftTypeRefBase, rightTypeRefBase);
}
/// <summary>
/// Subtract two constant objects.
/// Supported types are: string, bool, enum, decimal, double, float, ulong, long, uint, int, ushort, short, char, byte, sbyte.
/// </summary>
/// <returns>
/// The difference of the two constants, using the appropriate result type, including promoting smaller
/// types to int. Returns null if the operation is invalid.
/// </returns>
protected override object EvaluateConstants(object leftConstant, object rightConstant)
{
// Null, string, or boolean operands aren't supported
if (leftConstant == null || rightConstant == null || leftConstant is string || rightConstant is string
|| leftConstant is bool || rightConstant is bool)
return null;
// Handle enum constants
// Enumeration subtraction: If both sides are of the same enum type, then the result is
// the underlying type of the enum. If the left side is an enum and right is of the enums
// underlying type (or is implicitly convertible to it), then the result is the enum type.
if (leftConstant is EnumConstant)
{
EnumConstant leftEnumConstant = (EnumConstant)leftConstant;
if (rightConstant is EnumConstant)
{
EnumConstant rightEnumConstant = (EnumConstant)rightConstant;
if (leftEnumConstant.EnumTypeRef.IsSameRef(rightEnumConstant.EnumTypeRef))
{
// U -(E, E):
object enumResult = EvaluateConstants(leftEnumConstant.ConstantValue, rightEnumConstant.ConstantValue);
if (enumResult != null)
return TypeRef.ChangeTypeOfConstant(enumResult, leftEnumConstant.EnumTypeRef.GetUnderlyingTypeOfEnum());
}
}
else
{
TypeRefBase underlyingTypeRefBase = leftEnumConstant.EnumTypeRef.GetUnderlyingTypeOfEnum();
TypeRef rightTypeRef = new TypeRef(rightConstant.GetType());
if (rightTypeRef.IsImplicitlyConvertibleTo(underlyingTypeRefBase))
{
// E -(E, U):
object enumValue = EvaluateConstants(leftEnumConstant.ConstantValue, rightConstant);
if (enumValue != null)
return new EnumConstant(leftEnumConstant.EnumTypeRef, TypeRef.ChangeTypeOfConstant(enumValue, underlyingTypeRefBase));
}
}
return null; // Invalid result
}
// 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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