protected override void Visit(LogicalBindaryExpression exp)
{
// OR is the 3rd level
if (exp.Operator == LogicalOperator.OR)
{
// Simply visit the 3rd OR level and build all ComparisonModels
Visit(exp.Left);
Visit(exp.Right);
}
if (exp.Operator == LogicalOperator.AND)
{
// Because this class only build for ONE condition at a time.
// So if we encounter a AND expression, it must be the 2nd level, that is, the (ComparisonGroup AND ComparisonGroup) level
Visit(exp.Left);
BuildComparisonGroup();
Visit(exp.Right);
BuildComparisonGroup();
}
}
protected virtual void Visit(LogicalBindaryExpression exp)
{
Visit(exp.Left);
Visit(exp.Right);
}
void IExpressionVisitor.Visit(LogicalBindaryExpression exp)
{
Visit(exp);
}
void IExpressionVisitor.Visit(LogicalBindaryExpression exp)
{
Visit(exp);
}
protected virtual void Visit(LogicalBindaryExpression exp)
{
Visit(exp.Left);
Visit(exp.Right);
}
protected override void Visit(LogicalBindaryExpression exp)
{
Visit(exp.Left);
// Check if we can get result by only checking left expression.
// If yes, then the result in the stack is alreay the result.
var leftResult = _results.Peek();
// A and B, if A is false, the result will always be false, no need to check B
if (exp.Operator == LogicalOperator.AND && leftResult == false)
{
return;
}
// A or B, if A is true, the result will always be true, no need to check B
if (exp.Operator == LogicalOperator.OR && leftResult == true)
{
return;
}
// Pop the result of the left expression
_results.Pop();
// If we cannot get result by checking left expression,
// then check right expression.
// The final result is same as the result of the right expression.
// For example,
// A and B, if A is true, then final result = B
// A or B, if A is false, then final result = B
Visit(exp.Right);
}
// term : factor [ AND factor ]
private Expression Term()
{
var exp = Factor();
if (exp != null)
{
while (!_tokenzier.IsEndOfFile)
{
using (var lookahead = _tokenzier.BeginLookahead())
{
var op = _tokenzier.NextToken();
if (op != null && op.Kind == TokenKind.AND)
{
var sourceLocation = _tokenzier.CurrentLocation;
var right = Factor();
if (right != null)
{
lookahead.Accept();
exp = new LogicalBindaryExpression(exp, right, LogicalOperator.AND);
}
else
{
_context.AddError("Missing right operand for operator " + op.Kind + ".", sourceLocation);
break;
}
}
else
{
break;
}
}
}
}
return exp;
}
