private Expression AndExpression()
{
Expression ret = EqualityExpression();
while (Current.Kind == TokenKind.OpAnd) {
Consume(); // Or
Expression rhs = EqualityExpression();
ret = new BinaryExpression(ret.Line, ret.Column, ret, TokenKind.OpAnd, rhs);
}
return ret;
}
private Expression EqualityExpression()
{
Expression ret = RelationalExpression();
while (Current.Kind == TokenKind.OpIs ||
Current.Kind == TokenKind.OpIsNot) {
Token tok = Consume(); // consume operator
Expression rhs = RelationalExpression();
ret = new BinaryExpression(ret.Line, ret.Column, ret, tok.Kind, rhs);
}
return ret;
}
private Expression RelationalExpression()
{
Expression ret = PrimaryExpression();
while (Current.Kind == TokenKind.OpLt ||
Current.Kind == TokenKind.OpLte ||
Current.Kind == TokenKind.OpGt ||
Current.Kind == TokenKind.OpGte) {
Token tok = Consume(); // consume operator
Expression rhs = PrimaryExpression();
ret = new BinaryExpression(ret.Line, ret.Column, ret, tok.Kind, rhs);
}
return ret;
}
private object EvaluateBinaryExpression(BinaryExpression expression)
{
switch (expression.Operator) {
case TokenKind.OpOr: {
object lhsValue = EvaluateExpression(expression.Left);
if (Util.ToBoolean(lhsValue))
return true;
object rhsValue = EvaluateExpression(expression.Right);
return Util.ToBoolean(rhsValue);
}
case TokenKind.OpAnd: {
object lhsValue = EvaluateExpression(expression.Left);
if (!Util.ToBoolean(lhsValue))
return false;
object rhsValue = EvaluateExpression(expression.Right);
return Util.ToBoolean(rhsValue);
}
case TokenKind.OpIs: {
object lhsValue = EvaluateExpression(expression.Left);
object rhsValue = EvaluateExpression(expression.Right);
return lhsValue.Equals(rhsValue);
}
case TokenKind.OpIsNot: {
object lhsValue = EvaluateExpression(expression.Left);
object rhsValue = EvaluateExpression(expression.Right);
return !lhsValue.Equals(rhsValue);
}
case TokenKind.OpGt: {
object lhsValue = EvaluateExpression(expression.Left);
object rhsValue = EvaluateExpression(expression.Right);
IComparable c1 = lhsValue as IComparable;
IComparable c2 = rhsValue as IComparable;
if (c1 == null || c2 == null)
return false;
return c1.CompareTo(c2) == 1;
}
case TokenKind.OpLt: {
object lhsValue = EvaluateExpression(expression.Left);
object rhsValue = EvaluateExpression(expression.Right);
IComparable c1 = lhsValue as IComparable;
IComparable c2 = rhsValue as IComparable;
if (c1 == null || c2 == null)
return false;
return c1.CompareTo(c2) == -1;
}
case TokenKind.OpGte: {
object lhsValue = EvaluateExpression(expression.Left);
object rhsValue = EvaluateExpression(expression.Right);
IComparable c1 = lhsValue as IComparable;
IComparable c2 = rhsValue as IComparable;
if (c1 == null || c2 == null)
return false;
return c1.CompareTo(c2) >= 0;
}
case TokenKind.OpLte: {
object lhsValue = EvaluateExpression(expression.Left);
object rhsValue = EvaluateExpression(expression.Right);
IComparable c1 = lhsValue as IComparable;
IComparable c2 = rhsValue as IComparable;
if (c1 == null || c2 == null)
return false;
return c1.CompareTo(c2) <= 0;
}
default:
throw new TemplateException("Operator " + expression.Operator.ToString() + " is not supported.", expression.Line,
expression.Column);
}
}
