private void Shift(StackGraph graph, GrammarRuleToken token)
{
List <Node> resultNodes = new List <Node>(graph.Heads.Count);
foreach (var head in graph.Heads)
{
if (Table[head.State].ShiftActionsMap.TryGetValue(token, out int nextState))
{
var newNode = new Node(token, nextState);
newNode.PrevNodes.Add(new Edge {
PrevNode = head, Meta = new ParseExplanation {
ResultToken = token, RuleApplied = null, ChildrenExplained = null
}
});
resultNodes.Add(newNode);
}
else if (Table.Grammar.IsSkipGrammar && Table[head.State].ShiftActionsMap.TryGetValue(Table.Grammar.SkipToken, out int skipState))
{
var newNode = new Node(token, nextState);
newNode.PrevNodes.Add(new Edge {
PrevNode = head, Meta = new ParseExplanation {
ResultToken = token, RuleApplied = null, ChildrenExplained = null
}
});
resultNodes.Add(newNode);
}
}
graph.Heads = CombineNodes(resultNodes).ToList();
}
public static Grammar Parse(string grammarAsText)
{
var lines =
grammarAsText
.Split(_lineSeparators, StringSplitOptions.RemoveEmptyEntries)
.Where(l => !string.IsNullOrWhiteSpace(l))
.Select(l => l.Trim())
.Where(l => !_commentPrefix.Any(prefix => l.StartsWith(prefix)))
.ToList();
Dictionary <string, GrammarRuleToken> knownTokens = new Dictionary <string, GrammarRuleToken>();
var skipDefinition = lines[0].Split(_tokenSeparators, StringSplitOptions.RemoveEmptyEntries);
bool isSkipGrammar = bool.Parse(skipDefinition[0]);
GrammarRuleToken skipToken = isSkipGrammar ? new GrammarRuleToken {
IsTerminal = true, Value = skipDefinition[1].Trim()
} : null;
var acceptingTokens = lines[1].Split(_tokenSeparators, StringSplitOptions.RemoveEmptyEntries).Select(t => ConvertStringToToken(t, knownTokens)).ToList();
var rules = lines.Skip(2).Select((str, index) => ConvertStringToRule(str, index, knownTokens)).ToList();
return(new Grammar
{
FinalTokens = new HashSet <GrammarRuleToken>(acceptingTokens),
Rules = rules,
IsSkipGrammar = isSkipGrammar,
SkipToken = skipToken
});
}
private static GrammarRuleToken ConvertStringToToken(string str, Dictionary <string, GrammarRuleToken> knownTokens)
{
str = str.Trim();
if (knownTokens.TryGetValue(str, out var existingToken))
{
return(existingToken);
}
var newToken = new GrammarRuleToken
{
IsTerminal = str.Any(c => char.IsLower(c) || !char.IsUpper(c)),
Value = str
};
knownTokens.Add(str, newToken);
return(newToken);
}
public Node(GrammarRuleToken token, int state)
{
Token = token;
State = state;
}
public virtual bool Matches(GrammarRuleToken otherToken)
{
return((IsTerminal == otherToken.IsTerminal) && (Value == otherToken.Value));
}
