public override SyntaxTreeNode Make(ObjectStream <MyToken> input, MyDiscardDelegate <MyToken> discarder)
{
Ensure(input, discarder);
// Ignora código descartável inicialmente
input.Discard(discarder);
if (input.EndOfStream())
{
return(null);
}
var initialPos = input.GetPosition();
// O primeiro token é só um marcador (etiqueta) pra indicar
// um elemento válido
var tag = input.Next();
if (tag == null || (CalcTwoNumbersTokenClass)tag.Class != (CalcTwoNumbersTokenClass)GetTokenClass())
{
input.SetPosition(initialPos);
return(null);
}
var numberLeftNode = ExpressionElements[0].Make(input, discarder);
var plusNode = ExpressionElements[1].Make(input, discarder);
var numberRightNode = ExpressionElements[2].Make(input, discarder);
if (numberLeftNode == null || plusNode == null || numberRightNode == null)
{
input.SetPosition(initialPos);
return(null);
}
var exprTreeNode = new SyntaxTreeNode();
plusNode.AddChildNode(numberLeftNode);
plusNode.AddChildNode(numberRightNode);
exprTreeNode.AddChildNode(plusNode);
return(exprTreeNode);
}
