private void CheckAndSetAlias(string alias, Terminal terminal, LexSpan span)
{
//
// Check if this alias already known.
//
if (aliasTerms.ContainsKey(alias))
{
//
// If an alias denotes more than one logical token then used
// occurrences of the literal string alias must be disallowed.
//
Terminal other = aliasTerms[alias];
if (other != terminal)
{
handler.AddWarning(153,
String.Format(CultureInfo.InvariantCulture,
"Alias \"{0}\" also used for previous token: {1}, used occurrences forbidden",
alias, other.BaseString()), span);
aliasTerms[alias] = Terminal.Ambiguous;
}
}
else
{
aliasTerms[alias] = terminal;
}
}
private void Walk(NonTerminal node, Stack <NonTerminal> stack, List <NonTerminal> fixes, ref int count)
{
count++;
stack.Push(node);
node.depth = count;
foreach (NonTerminal next in node.dependsOnList)
{
if (next.depth == 0)
{
Walk(next, stack, fixes, ref count);
}
if (next.depth < count)
{
node.depth = next.depth;
}
}
if (node.depth == count) // traversal leaving strongly connected component
{
// This algorithm is folklore. I have been using it since
// at least early 1980s in the Gardens Point compilers.
// I don't even remember where I learned it ... (kjg).
//
NonTerminal popped = stack.Pop();
popped.depth = finishMark;
if (popped != node)
{
List <NonTerminal> SCC = new List <NonTerminal>();
SCC.Add(popped);
do
{
popped = stack.Pop();
popped.depth = finishMark;
SCC.Add(popped);
}while (popped != node);
handler.AddWarning(150, String.Format(CultureInfo.InvariantCulture,
"The following {2} symbols form a non-terminating cycle {0}{{{1}}}",
System.Environment.NewLine,
ListUtilities.GetStringFromList(SCC),
SCC.Count), null);
//
// Check if termination of any single NonTerminal
// would eliminate the whole cycle of dependency.
//
SccExperiment(SCC, fixes);
}
}
count--;
}
// =============================================================================
#endregion Terminating Computation
// =============================================================================
internal bool CheckGrammar(ErrorHandler handler)
{
bool ok = true;
NonTerminal nt;
this.handler = handler;
MarkReachable();
MarkTerminating();
foreach (KeyValuePair <string, NonTerminal> pair in nonTerminals)
{
nt = pair.Value;
if (!nt.reached)
{
handler.AddWarning(152, String.Format(CultureInfo.InvariantCulture,
"NonTerminal symbol \"{0}\" is unreachable", pair.Key), null);
}
if (nt.productions.Count == 0)
{
ok = false;
handler.AddError(5, String.Format(CultureInfo.InvariantCulture,
"NonTerminal symbol \"{0}\" has no productions", pair.Key), null);
}
}
if (this.HasNonTerminatingNonTerms)
{
ok = false;
}
return(ok);
}
