public static IImmutableSet <Token> NextOf(this IFirstFollowProvider provider, PartialRule partialRule)
{
var firsts = provider.FirstOf(partialRule.Symbols);
return(firsts.ContainsDefault()
? firsts.RemoveDefault().Union(provider.FollowOf(partialRule.Rule))
: firsts);
}
public static IImmutableSet <Token> FirstOf(this IFirstFollowProvider provider, IEnumerable <Symbol> symbols)
{
var builder = ImmutableHashSet.CreateBuilder <Token>();
foreach (var symbol in symbols)
{
var firsts = provider.FirstOf(symbol);
builder.UnionWith(firsts.Where(s => s != null));
if (!firsts.ContainsDefault())
{
// not nullable
return(builder.ToImmutable());
}
}
// if we reach here, we're nullable
return(builder.ToImmutable().AddDefault());
}
public static IImmutableSet <Token> NextOf(this IFirstFollowProvider provider, Rule rule)
{
return(provider.NextOf(new PartialRule(rule)));
}
public static bool IsNullable(this IFirstFollowProvider provider, Symbol symbol)
{
return(symbol is NonTerminal && provider.FirstOf(symbol).Contains(null));
}
public InternalFirstFollowProvider(IFirstFollowProvider provider)
{
this.originalGrammarProvider = provider;
}
