/// <summary>
/// Builds and return an SLR(1) <see cref="ParserTable"/> based on the given paramaters.
/// </summary>
/// <param name="grammar">The grammar.</param>
/// <param name="canonical_sets">LR(0) canonical sets generated from the <paramref name="grammar"/>.</param>
/// <param name="follow_sets">Follow sets of all the <paramref name="grammar"/>'s grammaticals
/// (see <see cref="FollowSets"/>).</param>
/// <returns>An SLR(1) parser table.</returns>
public static ParserTable Build( ExtendedGrammar grammar, LR0CanonicalSets canonical_sets,
IDictionary<GrammaticalSymbol, ISet<TerminalSymbol>> follow_sets)
{
if( object.ReferenceEquals(grammar, null) )
throw new ArgumentNullException("grammar");
if( object.ReferenceEquals(canonical_sets, null) )
throw new ArgumentNullException("canonical_sets");
if( object.ReferenceEquals(follow_sets, null) )
throw new ArgumentNullException("follow_sets");
var table = new ParserTable(canonical_sets.Sets.Count, grammar.Terminals.Count, grammar.Grammaticals.Count);
for( int state_index = 0; state_index < canonical_sets.Sets.Count; ++state_index )
{
// Steps
foreach( var term in grammar.Terminals )
{
int next_state_index = canonical_sets.GetTransition(state_index, term);
if( next_state_index != -1 )
{
if( table.GetAction(state_index, grammar.IndexOf(term)).Type != ParserTable.ActionType.Error )
throw new ArgumentException("Grammar is not SLR(1)."); //TODO: custom exception with conflict info
table.SetAction(state_index, grammar.IndexOf(term), ParserTable.Action.Step(next_state_index));
}
}
// Gotos
foreach( var gram in grammar.Grammaticals )
{
int next_state_index = canonical_sets.GetTransition(state_index, gram);
if( next_state_index != -1 )
{
if( table.GetGoto(state_index, grammar.IndexOf(gram)) != -1 )
throw new ArgumentException("Grammar is not SLR(1)."); //TODO: custom exception with conflict info
table.SetGoto(state_index, grammar.IndexOf(gram), next_state_index);
}
}
// Reductions
foreach( var item in canonical_sets.Sets[state_index] )
if( item.CursorPosition == item.Rule.RightHandSide.Count )
{
// Is it [S'->S.] ?
if( item.Rule.LeftHandSide == grammar.StartSymbol )
{
if( table.GetAction(state_index, grammar.IndexOf(grammar.EndOfSourceSymbol)).Type != ParserTable.ActionType.Error )
throw new ArgumentException("Grammar is not SLR(1)."); //TODO: custom exception with conflict info
table.SetAction(
state_index,
grammar.IndexOf(grammar.EndOfSourceSymbol),
ParserTable.Action.Accept());
}
// ... no, it's [A->alpha.]
else
{
int rule_index = grammar.Rules.IndexOf(item.Rule);
foreach( var follow_term in follow_sets[item.Rule.LeftHandSide] )
{
if( table.GetAction(state_index, grammar.IndexOf(follow_term)).Type != ParserTable.ActionType.Error )
throw new ArgumentException("Grammar is not SLR(1)."); //TODO: custom exception with conflict info
table.SetAction(
state_index,
grammar.IndexOf(follow_term),
ParserTable.Action.Reduction(rule_index));
}
}
}
}
return table;
}
