static ICollection <LRItem> _FillLRMove(this CfgDocument cfg, IEnumerable <LRItem> itemSet, object input, IProgress <CfgLalr1Progress> progress, ICollection <LRItem> result = null)
{
if (null == result)
{
result = new HashSet <LRItem>();
}
int i = 0;
foreach (var item in itemSet)
{
if (null != progress)
{
progress.Report(new CfgLalr1Progress(CfgLalr1Status.ComputingMove, i));
}
var next = item.RightIndex < item.Rule.Right.Count ? item.Rule.Right[item.RightIndex] : null;
if (item.RightIndex < item.Rule.Right.Count)
{
if (Equals(next, input))
{
var lri = new LRItem(item.Rule, item.RightIndex + 1);
result.Add(lri);
}
}
++i;
}
_FillLRClosureInPlace(cfg, progress, result);
return(result);
}
public override void Apply(LanguageData language, LRItem owner)
{
//Create custom action and put it into state.Actions table
var state = owner.State;
var action = new CustomParserAction(language, state, _executeMethod);
_previewMethod?.Invoke(action);
if (!state.BuilderData.IsInadequate)
{
// adequate state, with a single possible action which is DefaultAction
state.DefaultAction = action;
}
else if (owner.Core.Current != null)
{
//shift action
state.Actions[owner.Core.Current] = action;
}
else
{
foreach (var lkh in owner.Lookaheads)
{
state.Actions[lkh] = action;
}
}
//We consider all conflicts handled by the action
state.BuilderData.Conflicts.Clear();
}
public override void Apply(LanguageData language, LRItem owner)
{
var state = owner.State;
var allConflicts = state.BuilderData.Conflicts;
if (allConflicts.Count == 0)
{
return;
}
//Find all conflicts that can be resolved by operator precedence
// SL does not support Find extension, so we do it with explicit loop
var operConflicts = allConflicts.Where(c => c.Flags.IsSet(TermFlags.IsOperator)).ToList();
foreach (var conflict in operConflicts)
{
var newState = state.BuilderData.GetNextState(conflict);
var reduceItems = state.BuilderData.ReduceItems.SelectByLookahead(conflict).ToList();
if (newState == null || reduceItems.Count != 1)
{
// This cannot be fixed by precedence
continue;
}
state.Actions[conflict] = new PrecedenceBasedParserAction(conflict, newState, reduceItems[0].Core.Production);
allConflicts.Remove(conflict);
}
}
public override void Apply(LanguageData language, LRItem owner) {
var state = owner.State;
var conflicts = state.BuilderData.Conflicts;
if (conflicts.Count == 0) return;
switch (ActionType) {
case PreferredActionType.Shift:
var currTerm = owner.Core.Current as Terminal;
if (currTerm == null || !conflicts.Contains(currTerm)) return; //nothing to do
//Current term for shift item (hint owner) is a conflict - resolve it with shift action
var newState = owner.ShiftedItem.State;
var shiftAction = new ShiftParserAction(owner);
state.Actions[currTerm] = shiftAction;
conflicts.Remove(currTerm);
return;
case PreferredActionType.Reduce:
if (!owner.Core.IsFinal) return; //we take care of reduce items only here
//we have a reduce item with "Reduce" hint. Check if any of lookaheads are in conflict
ReduceParserAction reduceAction = null;
foreach (var lkhead in owner.Lookaheads)
if (conflicts.Contains(lkhead)) {
if (reduceAction == null)
reduceAction = new ReduceParserAction(owner.Core.Production);
state.Actions[lkhead] = reduceAction;
conflicts.Remove(lkhead);
}
return;
}//switch
}//method
public override void Apply(LanguageData language, LRItem owner)
{
//Check that owner is not final - we can imply precedence only in shift context
var curr = owner.Core.Current;
if (curr == null)
return;
//mark the state, to make sure we do stuff in Term_Shifting event handler only in appropriate states
owner.State.CustomFlags |= ImpliedPrecedenceCustomFlag;
curr.Shifting += Term_Shifting;
}
public ReduceAction(ParseTable <T> table, LRItem <T> reduceItem)
: base(table)
{
if (reduceItem != null)
{
ReduceItem = reduceItem;
}
else
{
throw new ArgumentNullException("reduceItem", "Must be non-null");
}
}
public AcceptAction(ParseTable <T> table, LRItem <T> acceptItem)
: base(table)
{
if (acceptItem != null)
{
AcceptItem = acceptItem;
}
else
{
throw new ArgumentNullException("acceptItem", "Must be non-null");
}
}
public override void Apply(LanguageData language, LRItem owner)
{
//Check that owner is not final - we can imply precedence only in shift context
var curr = owner.Core.Current;
if (curr == null)
{
return;
}
//mark the state, to make sure we do stuff in Term_Shifting event handler only in appropriate states
owner.State.CustomFlags |= ParserStateFlags.ImpliedPrecedence;
curr.Shifting += Term_Shifting;
}
public override void Apply(LanguageData language, LRItem owner)
{
var state = owner.State;
var conflicts = state.BuilderData.Conflicts;
if (conflicts.Count == 0)
{
return;
}
switch (_actionType)
{
case PreferredActionType.Shift:
var currTerm = owner.Core.Current as Terminal;
if (currTerm == null || !conflicts.Contains(currTerm))
{
//nothing to do
return;
}
//Current term for shift item (hint owner) is a conflict - resolve it with shift action
var shiftAction = new ShiftParserAction(owner);
state.Actions[currTerm] = shiftAction;
conflicts.Remove(currTerm);
return;
case PreferredActionType.Reduce:
if (!owner.Core.IsFinal)
{
//we take care of reduce items only here
return;
}
//we have a reduce item with "Reduce" hint. Check if any of lookaheads are in conflict
ReduceParserAction reduceAction = null;
foreach (var lkhead in owner.Lookaheads)
{
if (conflicts.Contains(lkhead))
{
if (reduceAction == null)
{
reduceAction = new ReduceParserAction(owner.Core.Production);
}
state.Actions[lkhead] = reduceAction;
conflicts.Remove(lkhead);
}
}
return;
default:
throw new ArgumentOutOfRangeException();
}
}
//Creates closure items with "spontaneously generated" lookaheads
private bool AddClosureItems(ParserState state)
{
bool result = false;
//note that we change collection while we iterate thru it, so we have to use "for i" loop
for (int i = 0; i < state.Items.Count; i++)
{
LRItem item = state.Items[i];
BnfTerm currTerm = item.Core.Current;
if (currTerm == null || !(currTerm is NonTerminal))
{
continue;
}
//1. Add normal closure items
NtData currInfo = (NtData)currTerm.ParserData;
foreach (Production prod in currInfo.Productions)
{
LR0Item core = prod.LR0Items[0]; //item at zero index is the one that starts with dot
LRItem newItem = TryFindItem(state, core);
if (newItem == null)
{
newItem = new LRItem(state, core);
state.Items.Add(newItem);
result = true;
}
#region Comments on lookaheads processing
// The general idea of generating ("spontaneously") the lookaheads is the following:
// Let's the original item be in the form
// [A -> alpha . B beta , lset]
// where <B> is a non-terminal and <lset> is a set of lookaheads,
// <beta> is some string (B's tail in our terminology)
// Then the closure item on non-teminal B is an item
// [B -> x, firsts(beta + lset)]
// (the lookahead set is expression after the comma).
// To generate lookaheads on a closure item, we simply take "firsts"
// from the tail <beta> of the NonTerminal <B>.
// Normally if tail <beta> is nullable we would add ("propagate")
// the <lset> lookaheads from <A> to <B>.
// We dont' do it right here - we simply add a propagation link.
// We propagate all lookaheads later in a separate process.
#endregion
newItem.NewLookaheads.AddRange(item.Core.TailFirsts);
if (item.Core.TailIsNullable && !item.PropagateTargets.Contains(newItem))
{
item.PropagateTargets.Add(newItem);
}
} //foreach prod
} //for i (LRItem)
return(result);
}
public override void Apply(LanguageData language, LRItem owner)
{
//Create custom action and put it into state.Actions table
var state = owner.State;
var action = new CustomParserAction(language, state, _executeMethod);
if (_previewMethod != null)
_previewMethod(action);
if (!state.BuilderData.IsInadequate) // adequate state, with a single possible action which is DefaultAction
state.DefaultAction = action;
else if (owner.Core.Current != null) //shift action
state.Actions[owner.Core.Current] = action;
else
foreach (var lkh in owner.Lookaheads)
state.Actions[lkh] = action;
//We consider all conflicts handled by the action
state.BuilderData.Conflicts.Clear();
} //method
public override void Apply(LanguageData language, LRItem owner) {
var state = owner.State;
var allConflicts = state.BuilderData.Conflicts;
if (allConflicts.Count == 0)
return;
//Find all conflicts that can be resolved by operator precedence
// SL does not support Find extension, so we do it with explicit loop
var operConflicts = new List<Terminal>();
foreach(var c in allConflicts)
if (c.Flags.IsSet(TermFlags.IsOperator))
operConflicts.Add(c);
foreach (var conflict in operConflicts) {
var newState = state.BuilderData.GetNextState(conflict);
var reduceItem = state.BuilderData.ReduceItems.SelectByLookahead(conflict).First(); //should be only one
state.Actions[conflict] = new PrecedenceBasedParserAction(conflict, newState, reduceItem.Core.Production);
allConflicts.Remove(conflict);
}//foreach conflict
}
public override void Apply(LanguageData language, LRItem owner)
{
var state = owner.State;
if (!state.BuilderData.IsInadequate) return; //the state is adequate, we don't need to do anything
var conflicts = state.BuilderData.Conflicts;
// Note that we remove lookaheads from the state conflicts set at the end of this method - to let parser builder know
// that this conflict is taken care of.
// On the other hand we may call this method multiple times for different LRItems if we have multiple hints in the same state.
// Since we remove lookahead from conflicts on the first call, on the consequitive calls it will not be a conflict -
// but we still need to add a new conditional entry to a conditional parser action for this lookahead.
// Thus we process the lookahead anyway, even if it is not a conflict.
// if (conflicts.Count == 0) return; -- this is a wrong thing to do
switch (_actionType)
{
case PreferredActionType.Reduce:
if (!owner.Core.IsFinal) return;
//it is reduce action; find lookaheads in conflict
var lkhs = owner.Lookaheads;
if (lkhs.Count == 0) return; //if no conflicts then nothing to do
var reduceAction = new ReduceParserAction(owner.Core.Production);
var reduceCondEntry = new ConditionalParserAction.ConditionalEntry(CheckCondition, reduceAction,
_description);
foreach (var lkh in lkhs)
{
AddConditionalEntry(state, lkh, reduceCondEntry);
if (conflicts.Contains(lkh))
conflicts.Remove(lkh);
}
break;
case PreferredActionType.Shift:
var curr = owner.Core.Current as Terminal;
if (curr == null) return; //it is either reduce item, or curr is a NonTerminal - we cannot shift it
var shiftAction = new ShiftParserAction(owner);
var shiftCondEntry = new ConditionalParserAction.ConditionalEntry(CheckCondition, shiftAction,
_description);
AddConditionalEntry(state, curr, shiftCondEntry);
if (conflicts.Contains(curr))
conflicts.Remove(curr);
break;
}
} //method
private void CreateParserStates()
{
Data.States.Clear();
_stateHash = new ParserStateTable();
CreateInitialAndFinalStates();
string augmRootKey = Data.AugmentedRoot.Key;
// Iterate through states (while new ones are created) and create shift transitions and new states
for (int index = 0; index < Data.States.Count; index++)
{
ParserState state = Data.States[index];
AddClosureItems(state);
//Get keys of all possible shifts
ShiftTable shiftTable = GetStateShifts(state);
//Each key in shifts dict is an input element
// Value is LR0ItemList of shifted LR0Items for this input element.
foreach (string input in shiftTable.Keys)
{
LR0ItemList shiftedCoreItems = shiftTable[input];
ParserState newState = FindOrCreateState(shiftedCoreItems);
ActionRecord newAction = new ActionRecord(input, ParserActionType.Shift, newState, null);
state.Actions[input] = newAction;
//link original LRItems in original state to derived LRItems in newState
foreach (LR0Item coreItem in shiftedCoreItems)
{
LRItem fromItem = FindItem(state, coreItem.Production, coreItem.Position - 1);
LRItem toItem = FindItem(newState, coreItem.Production, coreItem.Position);
if (!fromItem.PropagateTargets.Contains(toItem))
{
fromItem.PropagateTargets.Add(toItem);
}
//copy hints from core items into the newAction
newAction.ShiftItems.Add(fromItem);
} //foreach coreItem
} //foreach input
} //for index
Data.FinalState = Data.InitialState.Actions[augmRootKey].NewState;
} //method
static void _FillLRClosureInPlace(CfgDocument cfg, IProgress <CfgLalr1Progress> progress, ICollection <LRItem> result)
{
var done = false;
while (!done)
{
done = true;
var l = result.ToArray();
for (var i = 0; i < l.Length; i++)
{
if (null != progress)
{
progress.Report(new CfgLalr1Progress(CfgLalr1Status.ComputingClosure, i));
}
var item = l[i];
var next = item.RightIndex < item.Rule.Right.Count ? item.Rule.Right[item.RightIndex] : null;
if (item.RightIndex < item.Rule.Right.Count)
{
if (cfg.IsNonTerminal(next))
{
for (int jc = cfg.Rules.Count, j = 0; j < jc; ++j)
{
var r = cfg.Rules[j];
if (r.Left == next)
{
var lri = new LRItem(r, 0);
if (!result.Contains(lri))
{
done = false;
result.Add(lri);
}
}
}
}
}
}
}
}
} //method
private void ResolveConflictByHints(ParserState state, Terminal conflict)
{
var stateData = state.BuilderData;
//reduce hints
var reduceItems = stateData.ReduceItems.SelectByLookahead(conflict);
foreach (var reduceItem in reduceItems)
{
if (reduceItem.Core.Hints.Find(h => h.HintType == HintType.ResolveToReduce) != null)
{
state.Actions[conflict] = new ParserAction(ParserActionType.Reduce, null, reduceItem.Core.Production);
state.BuilderData.ResolvedConflicts.Add(conflict);
return;
}
}
//shift hints
var shiftItems = stateData.ShiftItems.SelectByCurrent(conflict);
foreach (var shiftItem in shiftItems)
{
if (shiftItem.Core.Hints.Find(h => h.HintType == HintType.ResolveToShift) != null)
{
//shift action is already there
state.BuilderData.ResolvedConflicts.Add(conflict);
return;
}
}
//code hints
// first prepare data for conflict action: reduceProduction (for possible reduce) and newState (for possible shift)
var reduceProduction = reduceItems.First().Core.Production; //take first of reduce productions
ParserState newState = (state.Actions.ContainsKey(conflict) ? state.Actions[conflict].NewState : null);
// Get all items that might contain hints;
var allItems = new LRItemList();
allItems.AddRange(state.BuilderData.ShiftItems.SelectByCurrent(conflict));
allItems.AddRange(state.BuilderData.ReduceItems.SelectByLookahead(conflict));
// Scan all items and try to find hint with resolution type Code
foreach (var item in allItems)
{
if (item.Core.Hints.Find(h => h.HintType == HintType.ResolveInCode) != null)
{
state.Actions[conflict] = new ParserAction(ParserActionType.Code, newState, reduceProduction);
state.BuilderData.ResolvedConflicts.Add(conflict);
return;
}
}
//custom hints
// find custom grammar hints and build custom conflict resolver
var customHints = new List <CustomGrammarHint>();
var hintItems = new Dictionary <CustomGrammarHint, LRItem>();
LRItem defaultItem = null; // the first item with no hints
foreach (var item in allItems)
{
var hints = item.Core.Hints.OfType <CustomGrammarHint>();
foreach (var hint in hints)
{
customHints.Add(hint);
hintItems[hint] = item;
}
if (defaultItem == null && !hints.Any())
{
defaultItem = item;
}
}
// if there are custom hints, build conflict resolver
if (customHints.Count > 0)
{
state.Actions[conflict] = new ParserAction(newState, reduceProduction, args => {
// examine all custom hints and select the first production that matched
foreach (var customHint in customHints)
{
if (customHint.Match(args))
{
var item = hintItems[customHint];
// If the ReduceProduction was clear, then use the default production following the hints
if (args.ReduceProduction == null)
{
args.ReduceProduction = item.Core.Production;
}
return;
}
}
// no hints matched, select default LRItem
if (defaultItem != null)
{
args.ReduceProduction = defaultItem.Core.Production;
args.Result = args.NewShiftState != null ? ParserActionType.Shift : ParserActionType.Reduce;
return;
}
// prefer Reduce if Shift operation is not available
args.Result = args.NewShiftState != null ? ParserActionType.Shift : ParserActionType.Reduce;
// TODO: figure out what to do next
});
state.BuilderData.ResolvedConflicts.Add(conflict);
return;
}
}
public ShiftParserAction(LRItem item)
: this(item.Core.Current, item.ShiftedItem.State)
{
}
public ShiftParserAction(LRItem item) : this(item.Core.Current, item.ShiftedItem.State)
{
}
/// <summary> Gives a chance to a custom code in hint to interfere in parser automaton construction.</summary>
/// <param name="language">The LanguageData instance.</param>
/// <param name="owner">The <see cref="LRItem"/> that "owns" the hint. </param>
/// <remarks>
/// The most common purpose of this method (it's overrides) is to resolve the conflicts
/// by adding specific actions into State.Actions dictionary.
/// The owner parameter represents the position in the grammar expression where the hint
/// is found. The parser state is available through owner.State property.
/// </remarks>
public virtual void Apply(LanguageData language, LRItem owner)
{
// owner.State -- the parser state
// owner.State.BuilderData.Conflicts -- as set of conflict terminals
// owner.State.Actions -- a dictionary of actions in the current state.
}
public override void Apply(LanguageData language, LRItem owner)
{
var state = owner.State;
if (!state.BuilderData.IsInadequate)
{
return; //the state is adequate, we don't need to do anything
}
var conflicts = state.BuilderData.Conflicts;
// Note that we remove lookaheads from the state conflicts set at the end of this method - to let parser builder know
// that this conflict is taken care of.
// On the other hand we may call this method multiple times for different LRItems if we have multiple hints in the same state.
// Since we remove lookahead from conflicts on the first call, on the consequitive calls it will not be a conflict -
// but we still need to add a new conditional entry to a conditional parser action for this lookahead.
// Thus we process the lookahead anyway, even if it is not a conflict.
// if (conflicts.Count == 0) return; -- this is a wrong thing to do
switch (_actionType)
{
case PreferredActionType.Reduce:
if (!owner.Core.IsFinal)
{
return;
}
//it is reduce action; find lookaheads in conflict
var lkhs = owner.Lookaheads;
if (lkhs.Count == 0)
{
return; //if no conflicts then nothing to do
}
var reduceAction = new ReduceParserAction(owner.Core.Production);
var reduceCondEntry = new ConditionalParserAction.ConditionalEntry(CheckCondition, reduceAction, _description);
foreach (var lkh in lkhs)
{
AddConditionalEntry(state, lkh, reduceCondEntry);
if (conflicts.Contains(lkh))
{
conflicts.Remove(lkh);
}
}
break;
case PreferredActionType.Shift:
var curr = owner.Core.Current as Terminal;
if (curr == null)
{
return; //it is either reduce item, or curr is a NonTerminal - we cannot shift it
}
var shiftAction = new ShiftParserAction(owner);
var shiftCondEntry = new ConditionalParserAction.ConditionalEntry(CheckCondition, shiftAction, _description);
AddConditionalEntry(state, curr, shiftCondEntry);
if (conflicts.Contains(curr))
{
conflicts.Remove(curr);
}
break;
default:
throw new ArgumentOutOfRangeException();
}
}
protected override LRItemSetCollection ComputeItemSetCollection()
{
var(collection, gotoSymbol) = ComputeLR0ItemSetKernelsCollectionAndGotoLookup();
// Determine propagation of lookaheads, and initialze lookaheads based on spontaneous generation
// (page 270-275, dragon book 2nd ed.)
collection.StartState.Single().Lookaheads.Add(Eof);
var rulePropagations = new Dictionary <(int state, LRItem item), HashSet <(int state, LRItem item)> >();
// For all states
foreach (var itemset in collection)
{
var gotosForState = gotoSymbol[itemset.Index];
// For every kernel item
foreach (var kernelitem in itemset)
{
var itemKey = (state : itemset.Index, item : kernelitem);
// Create an item set with a dummy lookahead.
// This dummy item set is based on the current state (current item set).
var dummyLookahead = Unknown.AsSingletonEnumerable();
var dummyItem = new LRItem(kernelitem.Rule, kernelitem.Marker, dummyLookahead);
var dummyItemSet = new LRItemSet(dummyItem.AsSingletonEnumerable());
var j = LR1Closure(dummyItemSet);
// For every symbol/state in the goto list
foreach (var gotokvp in gotosForState)
{
// What would be the next state?
var gotoItemSet = collection[gotokvp.Value];
var gotoItemLookup = gotoItemSet.ToDictionary(g => g, g => g);
// Find the items in the dummy set with the marker before this symbol.
foreach (var b in j.Where(bb => bb.Marker < bb.Length && bb.Rule.Symbols[bb.Marker].Equals(gotokvp.Key)))
{
// Get the item corresponding to the goto state with the marker advanced over the current symbol.
var gotoItem = gotoItemLookup[new LRItem(b.Rule, b.Marker + 1)];
// Note if lookaheads are propagated to the next item
if (b.Lookaheads.Any(l => l.CompareTo(Unknown) == 0))
{
if (!rulePropagations.ContainsKey(itemKey))
{
rulePropagations[itemKey] = new HashSet <(int, LRItem)>();
}
rulePropagations[itemKey].Add((gotoItemSet.Index, gotoItem));
}
gotoItem.Lookaheads.UnionWith(
b.Lookaheads.Where(l => l.CompareTo(Unknown) != 0)
);
}
}
}
}
bool changed;
do
{
changed = false;
foreach (var state in collection)
{
foreach (var item in state)
{
var itemKey = (state.Index, item);
if (!rulePropagations.TryGetValue(itemKey, out var propagated))
{
continue;
}
foreach (var key in propagated)
{
if (key.item.Lookaheads.TryUnionWith(item.Lookaheads))
{
changed = true;
}
}
}
}
} while (changed);
// Close all the kernels
for (var i = 0; i < collection.Count; i++)
{
collection[i] = LR1Closure(collection[i]);
collection[i].Index = i;
}
return(collection);
}