private Expression _RelationalExpression()
{
Expression ret = _PrimaryExpression();
while (Current.TokenKind == TokenKind.OpLt
|| Current.TokenKind == TokenKind.OpLte
|| Current.TokenKind == TokenKind.OpGt
|| Current.TokenKind == TokenKind.OpGte)
{
Token tok = _Consume(); // consume operator
Expression rhs = _PrimaryExpression();
ret = new BinaryExpression(ret.Line, ret.Col, ret, tok.TokenKind, rhs);
}
return ret;
}
private Expression _AndExpression()
{
Expression ret = _EqualityExpression();
while (Current.TokenKind == TokenKind.OpAnd)
{
_Consume(); // Or
Expression rhs = _EqualityExpression();
ret = new BinaryExpression(ret.Line, ret.Col, ret, TokenKind.OpAnd, rhs);
}
return ret;
}
private Expression _EqualityExpression()
{
Expression ret = _RelationalExpression();
while (Current.TokenKind == TokenKind.OpIs
|| Current.TokenKind == TokenKind.OpIsNot)
{
Token tok = _Consume(); // consume operator
Expression rhs = _RelationalExpression();
ret = new BinaryExpression(ret.Line, ret.Col, ret, tok.TokenKind, rhs);
}
return ret;
}
/// <summary>
/// 执行预定义运算符，并返回执行结果。
/// </summary>
/// <param name="exp">指定一个预定义运算符。</param>
/// <returns>object</returns>
protected object EvalBinaryExpression(BinaryExpression exp)
{
switch (exp.Operator)
{
case TokenKind.OpOr:
{
object lhsValue = this.EvalExpression(exp.Lhs);
if (Utility.ToBool(lhsValue))
return true;
object rhsValue = this.EvalExpression(exp.Rhs);
return Utility.ToBool(rhsValue);
}
case TokenKind.OpAnd:
{
object lhsValue = this.EvalExpression(exp.Lhs);
if (!Utility.ToBool(lhsValue))
return false;
object rhsValue = this.EvalExpression(exp.Rhs);
return Utility.ToBool(rhsValue);
}
case TokenKind.OpIs:
{
object lhsValue = this.EvalExpression(exp.Lhs);
object rhsValue = this.EvalExpression(exp.Rhs);
return lhsValue.Equals(rhsValue);
}
case TokenKind.OpIsNot:
{
object lhsValue = this.EvalExpression(exp.Lhs);
object rhsValue = this.EvalExpression(exp.Rhs);
return !lhsValue.Equals(rhsValue);
}
case TokenKind.OpGt:
{
object lhsValue = this.EvalExpression(exp.Lhs);
object rhsValue = this.EvalExpression(exp.Rhs);
IComparable c1 = lhsValue as IComparable;
IComparable c2 = rhsValue as IComparable;
if (c1 == null || c2 == null)
return false;
else
return c1.CompareTo(c2) == 1;
}
case TokenKind.OpLt:
{
object lhsValue = this.EvalExpression(exp.Lhs);
object rhsValue = this.EvalExpression(exp.Rhs);
IComparable c1 = lhsValue as IComparable;
IComparable c2 = rhsValue as IComparable;
if (c1 == null || c2 == null)
return false;
else
return c1.CompareTo(c2) == -1;
}
case TokenKind.OpGte:
{
object lhsValue = this.EvalExpression(exp.Lhs);
object rhsValue = this.EvalExpression(exp.Rhs);
IComparable c1 = lhsValue as IComparable;
IComparable c2 = rhsValue as IComparable;
if (c1 == null || c2 == null)
return false;
else
return c1.CompareTo(c2) >= 0;
}
case TokenKind.OpLte:
{
object lhsValue = this.EvalExpression(exp.Lhs);
object rhsValue = this.EvalExpression(exp.Rhs);
IComparable c1 = lhsValue as IComparable;
IComparable c2 = rhsValue as IComparable;
if (c1 == null || c2 == null)
return false;
else
return c1.CompareTo(c2) <= 0;
}
default:
throw new TemplateRuntimeException("遭遇未受支持的运算符：" + exp.Operator.ToString(), exp.Line, exp.Col);
}
}