internal void CreateSpecialProduction(NonTerminal root)
{
rootProduction = new Production(LookupNonTerminal("$accept"));
AddProduction(rootProduction);
rootProduction.rhs.Add(root);
rootProduction.rhs.Add(LookupTerminal(Token.ident, "EOF"));
}
private List <NonTerminal> BuildDependencyGraph()
{
List <NonTerminal> rslt = new List <NonTerminal>();
foreach (KeyValuePair <string, NonTerminal> kvp in this.nonTerminals)
{
NonTerminal nonTerm = kvp.Value;
NonTerminal dependency = null;
if (!nonTerm.terminating)
{
rslt.Add(nonTerm);
nonTerm.dependsOnList = new List <NonTerminal>();
foreach (Production prod in nonTerm.productions)
{
foreach (Symbol symbol in prod.rhs)
{
dependency = symbol as NonTerminal;
if (dependency != null &&
dependency != nonTerm &&
!dependency.terminating &&
!nonTerm.dependsOnList.Contains(dependency))
{
nonTerm.depth = 0;
nonTerm.dependsOnList.Add(dependency);
}
}
}
}
}
return(rslt);
}
private static void SccPropagate(NonTerminal root, List <NonTerminal> thisTestConfig, List <NonTerminal> fixes)
{
int count = 0;
bool changed = false;
do
{
count = 0;
changed = false;
foreach (NonTerminal nt in thisTestConfig)
{
if (!nt.terminating)
{
foreach (Production prod in nt.productions)
{
if (ProductionTerminates(prod))
{
nt.terminating = true;
changed = true;
}
}
if (!nt.terminating)
{
count++;
}
}
}
}while (changed);
if (count == 0)
{
fixes.Add(root);
}
}
void WriteProductions(StreamWriter writer)
{
NonTerminal lhs = null;
foreach (Production production in productions)
{
int lhsLength = production.lhs.ToString().Length;
if (production.lhs != lhs)
{
lhs = production.lhs;
writer.WriteLine();
writer.Write("{0} {1}: ", ProductionAnchor(production.num), lhs);
}
else
{
writer.Write("{0} {1}| ", ProductionAnchor(production.num), new string(' ', lhsLength));
}
if (production.rhs.Count == 0)
{
writer.WriteLine("/* empty */");
}
else
{
writer.WriteLine(ListUtilities.GetStringFromList(production.rhs, " ", lhsLength + 12));
}
}
writer.WriteLine();
}
private void ComputeLA()
{
// LA(q, A->w) = Union { Follow(p,A) | p -> w -> q }
foreach (AutomatonState q in states)
{
foreach (ProductionItem item in q.allItems)
{
if (item.isReduction())
{
item.LA = new SetCollection <Terminal>();
foreach (AutomatonState p in states)
{
if (PathTo(p, item.production, item.pos) == q)
{
NonTerminal A = item.production.lhs;
if (p.nonTerminalTransitions.ContainsKey(A))
{
Transition pA = p.nonTerminalTransitions[A];
item.LA.AddRange(pA.Follow);
}
}
}
}
}
}
}
private void ComputeIncludes()
{
// (p,A) include (q,B) iff B -> Beta A Gamma and Gamma => empty and q -> Beta -> p
foreach (AutomatonState q in states)
{
foreach (Transition qB in q.nonTerminalTransitions.Values)
{
foreach (Production prod in qB.A.productions)
{
for (int i = prod.rhs.Count - 1; i >= 0; i--)
{
Symbol A = prod.rhs[i];
NonTerminal NT = A as NonTerminal;
if (NT != null)
{
AutomatonState p = PathTo(q, prod, i);
p.nonTerminalTransitions[NT].includes.Add(qB);
}
if (!A.IsNullable())
{
break;
}
}
}
}
}
}
internal NonTerminal LookupNonTerminal(string name)
{
if (!nonTerminals.ContainsKey(name))
{
nonTerminals[name] = new NonTerminal(name);
}
return(nonTerminals[name]);
}
private void LeafExperiment(NonTerminal probe, List <NonTerminal> component)
{
// Test what happens with probe terminating ...
probe.terminating = true;
LeafPropagate(probe, component);
// Then reset the values of all components
foreach (NonTerminal element in component)
{
element.terminating = false;
}
}
private static bool ProductionTerminates(Production thisProd)
{
foreach (Symbol smbl in thisProd.rhs)
{
NonTerminal nonTerm = smbl as NonTerminal;
if (nonTerm != null && !nonTerm.terminating)
{
return(false);
}
}
return(true);
}
/// <summary>
/// This is the method that computes the shortest terminal
/// string sequence for each NonTerminal symbol. The immediate
/// guide is to find those NT that are non-terminating.
/// </summary>
void MarkTerminating()
{
bool changed = false;
int nonTerminatingCount = 0;
// This uses a naive algorithm that iterates until
// an iteration completes without changing anything.
do
{
changed = false;
nonTerminatingCount = 0;
foreach (KeyValuePair <string, NonTerminal> kvp in this.nonTerminals)
{
NonTerminal nonTerm = kvp.Value;
if (!nonTerm.terminating)
{
foreach (Production prod in nonTerm.productions)
{
if (ProductionTerminates(prod))
{
nonTerm.terminating = true;
changed = true;
}
}
if (!nonTerm.terminating)
{
nonTerminatingCount++;
}
}
}
} while (changed);
//
// Now produce some helpful diagnostics.
// We wish to find single NonTerminals that, if made
// terminating will fix up many, even all of the
// non-terminating NonTerminals that have been found.
//
if (nonTerminatingCount > 0)
{
List <NonTerminal> ntDependencies = BuildDependencyGraph();
hasNonTerminatingNonTerms = true;
handler.AddError(
5,
String.Format(CultureInfo.InvariantCulture, "There are {0} non-terminating NonTerminal Symbols{1} {{{2}}}",
nonTerminatingCount,
System.Environment.NewLine,
ListUtilities.GetStringFromList(ntDependencies)), null);
FindNonTerminatingSCC(ntDependencies); // Do some diagnosis
}
}
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--;
}
private void LeafPropagate(NonTerminal root, List <NonTerminal> thisTestConfig)
{
int count = 0;
bool changed = false;
do
{
count = 0;
changed = false;
foreach (NonTerminal nt in thisTestConfig)
{
if (!nt.terminating)
{
foreach (Production prod in nt.productions)
{
if (ProductionTerminates(prod))
{
nt.terminating = true;
changed = true;
}
}
if (!nt.terminating)
{
count++;
}
}
}
}while (changed);
List <NonTerminal> filtered = FilterTerminatingElements(thisTestConfig);
handler.AddWarning(151, String.Format(CultureInfo.InvariantCulture,
"Terminating {0} fixes the following size-{1} NonTerminal set{2}{{{3}}}",
root.ToString(),
filtered.Count,
System.Environment.NewLine,
ListUtilities.GetStringFromList(filtered)), null);
}
void WriteProductions(StreamWriter writer)
{
NonTerminal lhs = null;
string padding = "";
foreach (Production production in productions)
{
int lhsLength = 0;
if (production.lhs != lhs)
{
if (lhs != null) // ==> this is a change to a new LHS, write terminating ';'
{
writer.WriteLine("{0} {1};", indexSkip, padding);
}
lhsLength = production.lhs.ToString().Length;
padding = new string( ' ', lhsLength );
lhs = production.lhs;
writer.WriteLine();
writer.Write("{0} {1}: ", ProductionAnchor(production.num), lhs);
}
else
{
writer.Write("{0} {1}| ", ProductionAnchor(production.num), padding);
}
if (production.rhs.Count == 0)
{
writer.WriteLine("/* empty */");
}
else
{
writer.WriteLine(ListUtilities.GetStringFromList(production.rhs, " ", lhsLength + 12));
}
}
writer.Write("{0} {1};", indexSkip, padding);
writer.WriteLine();
}
void MarkReachable()
{
Stack <NonTerminal> work = new Stack <NonTerminal>();
rootProduction.lhs.reached = true; // by definition.
work.Push(startSymbol);
startSymbol.reached = true;
while (work.Count > 0)
{
NonTerminal nonT = work.Pop();
foreach (Production prod in nonT.productions)
{
foreach (Symbol smbl in prod.rhs)
{
NonTerminal rhNt = smbl as NonTerminal;
if (rhNt != null && !rhNt.reached)
{
rhNt.reached = true;
work.Push(rhNt);
}
}
}
}
}
internal Production(NonTerminal lhs)
{
this.lhs = lhs;
lhs.productions.Add(this);
}
internal Transition(NonTerminal A, AutomatonState next)
{
this.A = A;
this.next = next;
}
internal Transition(NonTerminal A, AutomatonState next)
{
this.A = A;
this.next = next;
}
internal Production(NonTerminal lhs)
{
this.lhs = lhs;
lhs.productions.Add(this);
}