// generator is the non-terminal placed at the end of the chunk
// such non-terminal generates what can follow it, which can contain also non-terminal at the end
// which generates...
// ...until we get the length of required lookahead count
public FollowSets <SYMBOL_ENUM> ComputeFollowSets()
{
followSets = new FollowSets <SYMBOL_ENUM>(lookaheadWidth);
// fill all symbols with initially empty follow set
foreach (SYMBOL_ENUM symbol in nonTerminals.Concat(terminals))
{
followSets.Add(symbol, new SymbolChunkSet <SYMBOL_ENUM>());
}
followSets[startSymbol].Add(SymbolChunk.CreateRepeat(eofSymbol, lookaheadWidth));
foreach (SYMBOL_ENUM symbol in nonTerminals.Concat(terminals))
{
bootstrapFromFirstSets(symbol);
}
// each chunk can have only terminals, or terminals + 1 non terminal at the end (as FollowSet tail generator)
resolveFollowSetsDependencies();
// removal of follow sets "generators"
foreach (SymbolChunkSet <SYMBOL_ENUM> fset in followSets.Values)
{
fset.RemoveWhere(chunk => nonTerminals.Contains(chunk.Symbols.Last()));
}
return(followSets);
}
public BuilderHorizonSets(Productions <SYMBOL_ENUM, TREE_NODE> productions, int lookaheadWidth,
FirstSets <SYMBOL_ENUM> firstSets,
CoverSets <SYMBOL_ENUM> coverSets,
FollowSets <SYMBOL_ENUM> followSets)
: base(productions, lookaheadWidth)
{
this.firstSets = firstSets;
this.followSets = followSets;
this.coverSets = coverSets;
if (!coverSets.HasNonTerminals || lookaheadWidth != coverSets.LookaheadWidth)
{
throw new ArgumentException("Internal error.");
}
}
