/// <summary>
/// Creates and returns the LR(0) canonical sets for the given <paramref name="grammar"/>.
/// </summary>
/// <param name="grammar">The grammar to build the canonical sets for.</param>
/// <returns>The built canonical sets.</returns>
/// <exception cref="ArgumentNullException"> if <paramref name="grammar"/> is <c>null</c>.</exception>
public static LR0CanonicalSets Build( RestrictedStartSymbolGrammar grammar )
{
if( grammar == null )
throw new ArgumentNullException("grammar");
var terms_and_gramms = new List<Symbol>();
terms_and_gramms.AddRange(grammar.Grammaticals);
terms_and_gramms.AddRange(grammar.Terminals);
var sets = new LR0CanonicalSets();
// Calculate the I0 canonical set from the 'starting' rule
var s0 = new HashSet<LR0Item>();
if( grammar.Rules.Count > 0 )
s0.Add(new LR0Item(grammar.StartRule, 0));
var I0 = Closure(s0, grammar);
sets.Add(I0);
// Generate LR0CanonicalSets with Read()
for( int current_set_id = 0; current_set_id < sets.Sets.Count; ++current_set_id )
// Generate new sets for every symbol read
foreach( var symbol in terms_and_gramms )
{
var new_I = Read(sets.Sets[current_set_id], symbol, grammar);
// If the set is empty then continue
if( new_I.Count == 0 )
continue;
// Identify new_I
int next_set_id = sets.IndexOf(new_I);
// If this is a new CanonicalSet then add to the group
if( next_set_id == -1 )
next_set_id = sets.Add(new_I);
// Record the state transition
sets.SetTransition(current_set_id, symbol, next_set_id);
}
return sets;
}
