private ParseExplanation BuildParseRuleExplanation(PathBack pathBack, GrammarRule rule)
{
return(new ParseExplanation
{
RuleApplied = rule,
ResultToken = rule.ResultToken,
ChildrenExplained = pathBack.pathNodes.Select(pn => pn.incomingEdge.Meta).ToList()
});
}
private List <PathBack> FindAllPathsBack(Node head, int length)
{
List <PathBack> paths = new List <PathBack>();
Stack <StackFrame> stack = new Stack <StackFrame>();
stack.Push(new StackFrame {
currentDepth = 1, currentNode = head, nextParentId = 0
});
while (stack.Count > 0)
{
var frame = stack.Peek();
if (frame.currentDepth == length)
{
var pathBack = new PathBack
{
previousNode = frame.currentNode,
pathNodes = stack.Skip(1).Select(fr => new NodeWithIncomingEdge {
targetNode = fr.currentNode, incomingEdge = fr.currentNode.PrevNodes[fr.nextParentId]
}).ToList()
};
paths.Add(pathBack);
stack.Pop();
if (stack.Count > 0)
{
stack.Peek().nextParentId++;
}
continue;
}
else
{
if (frame.nextParentId >= frame.currentNode.PrevNodes.Count)
{
stack.Pop();
if (stack.Count > 0)
{
stack.Peek().nextParentId++;
}
continue;
}
else
{
stack.Push(new StackFrame {
currentDepth = frame.currentDepth + 1, currentNode = frame.currentNode.PrevNodes[frame.nextParentId].PrevNode, nextParentId = 0
});
continue;
}
}
}
return(paths);
}
private Node CreateReduceNode(PathBack pathBack, GrammarRule rule)
{
if (!Table[pathBack.previousNode.State].ShiftActionsMap.TryGetValue(rule.ResultToken, out int newState))
{
// after we reduced, there is no non-terminal-shift available. let's return null as a new node to signify no parse available
return(null);
}
var result = new Node(rule.ResultToken, newState);
result.PrevNodes.Add(new Edge {
PrevNode = pathBack.previousNode, Meta = BuildParseRuleExplanation(pathBack, rule)
});
return(result);
}
