/// <summary>
/// Accepts between <code>min</code> and <code>max</code> (including both) concatenated
/// repetitions of the language of the given automaton.
/// </summary>
/// <param name="a">The automaton.</param>
/// <param name="min">The minimum concatenated repetitions of the language of the given
/// automaton.</param>
/// <param name="max">The maximum concatenated repetitions of the language of the given
/// automaton.</param>
/// <returns>
/// Returns an automaton that accepts between <code>min</code> and <code>max</code>
/// (including both) concatenated repetitions of the language of the given automaton.
/// </returns>
/// <remarks>
/// Complexity: linear in number of states and in <code>min</code> and <code>max</code>.
/// </remarks>
internal static Automaton Repeat(Automaton a, int min, int max)
{
if (min > max)
{
return(BasicAutomata.MakeEmpty());
}
max -= min;
a.ExpandSingleton();
Automaton b;
if (min == 0)
{
b = BasicAutomata.MakeEmptyString();
}
else if (min == 1)
{
b = a.Clone();
}
else
{
var @as = new List <Automaton>();
while (min-- > 0)
{
@as.Add(a);
}
b = BasicOperations.Concatenate(@as);
}
if (max > 0)
{
Automaton d = a.Clone();
while (--max > 0)
{
Automaton c = a.Clone();
foreach (State p in c.GetAcceptStates())
{
p.AddEpsilon(d.Initial);
}
d = c;
}
foreach (State p in b.GetAcceptStates())
{
p.AddEpsilon(d.Initial);
}
b.IsDeterministic = false;
b.ClearHashCode();
b.CheckMinimizeAlways();
}
return(b);
}
internal static Automaton Concatenate(IList <Automaton> l)
{
if (l.Count == 0)
{
return(BasicAutomata.MakeEmptyString());
}
bool allSingleton = l.All(a => a.IsSingleton);
if (allSingleton)
{
var b = new StringBuilder();
foreach (Automaton a in l)
{
b.Append(a.Singleton);
}
return(BasicAutomata.MakeString(b.ToString()));
}
else
{
if (l.Any(a => a.IsEmpty))
{
return(BasicAutomata.MakeEmpty());
}
var ids = new HashSet <int>();
foreach (Automaton a in l)
{
ids.Add(RuntimeHelpers.GetHashCode(a));
}
bool hasAliases = ids.Count != l.Count;
Automaton b = l[0];
b = hasAliases ? b.CloneExpanded() : b.CloneExpandedIfRequired();
var ac = b.GetAcceptStates();
bool first = true;
foreach (Automaton a in l)
{
if (first)
{
first = false;
}
else
{
if (a.IsEmptyString())
{
continue;
}
Automaton aa = a;
aa = hasAliases ? aa.CloneExpanded() : aa.CloneExpandedIfRequired();
HashSet <State> ns = aa.GetAcceptStates();
foreach (State s in ac)
{
s.Accept = false;
s.AddEpsilon(aa.Initial);
if (s.Accept)
{
ns.Add(s);
}
}
ac = ns;
}
}
b.IsDeterministic = false;
b.ClearHashCode();
b.CheckMinimizeAlways();
return(b);
}
}
