//Create reduce actions for states with a single reduce item (and no shifts)
private void CreateRemainingReduceActions()
{
foreach (var state in _data.States)
{
if (state.DefaultAction != null)
{
continue;
}
var stateData = state.BuilderData;
if (stateData.ShiftItems.Count == 0 && stateData.ReduceItems.Count == 1)
{
state.DefaultAction = ReduceParserAction.Create(stateData.ReduceItems.First().Core.Production);
continue; //next state; if we have default reduce action, we don't need to fill actions dictionary for lookaheads
}
//create actions
foreach (var item in state.BuilderData.ReduceItems)
{
var action = ReduceParserAction.Create(item.Core.Production);
foreach (var lkh in item.Lookaheads)
{
if (state.Actions.ContainsKey(lkh))
{
continue;
}
state.Actions[lkh] = action;
}
} //foreach item
} //foreach state
}
public CustomParserAction(LanguageData language, ParserState state, ExecuteActionMethod executeRef)
{
Language = language;
State = state;
ExecuteRef = executeRef ?? throw new ArgumentNullException(nameof(executeRef));
Conflicts.UnionWith(state.BuilderData.Conflicts);
// Create default shift and reduce actions
foreach (var shiftItem in state.BuilderData.ShiftItems)
{
ShiftActions.Add(new ShiftParserAction(shiftItem));
}
foreach (var item in state.BuilderData.ReduceItems)
{
ReduceActions.Add(ReduceParserAction.Create(item.Core.Production));
}
}
//Find an LR item without hints compatible with term (either shift on term or reduce with term as lookahead);
// this item without hints would become our default. We assume that other items have hints, and when conditions
// on all these hints fail, we chose this remaining item without hints.
private static ParserAction FindDefaultAction(ParserState state, BnfTerm term)
{
//First check reduce items
var reduceItems = state.BuilderData.ReduceItems.SelectByLookahead(term as Terminal);
foreach (var item in reduceItems)
{
if (item.Core.Hints.Count == 0)
{
return(ReduceParserAction.Create(item.Core.Production));
}
}
var shiftItem = state.BuilderData.ShiftItems.SelectByCurrent(term).FirstOrDefault();
if (shiftItem != null)
{
return(new ShiftParserAction(shiftItem));
}
//if everything failed, returned first reduce item
return(null);
}