public NondeterministicFiniteAutomaton(States q, Alphabet a, NondeterministicTransitionFunction d, State q0,
AcceptingStates f) : base(q, a, d, q0, f)
{
Transitions = d;
}
private async Task <bool> Run(char[] x, State p, int i)
{
for (; i < x.Length; i++)
{
if (!Alphabet.Contains(x[i]))
{
return(false);
}
if (x[i] == Alphabet.EmptyString)
{
continue;
}
// get possible transitions
var q = Transitions[p, x[i]];
if (q.Length == 0) // nothing to do, stop
{
return(false);
}
if (q.Length == 1)
{
p = q[0].Q; // switch states
if (q[0].A == Alphabet.EmptyString)
{
i--; // Don't increment on null transition!
}
}
else // we have a choice
{
var tasks = new Task <bool> [q.Length];
// check each path asynchronously
for (var j = 0; j < q.Length; j++)
{
tasks[j] = Run(x, q[j].Q, q[j].A == Alphabet.EmptyString ? i : i + 1);
}
var result = false;
// check the result
foreach (var t in tasks)
{
result = result || await t;
}
return(result); // if one of them is successful, this branch accepts
}
}
// No more moves!
if (p.Accepting)
{
return(true);
}
// check for lambda transitions
var r = Transitions[p, Alphabet.EmptyString];
var lambdas = new Task <bool> [r.Length];
for (var k = 0; k < r.Length; k++)
{
lambdas[k] = Run(x, r[k].Q, i);
}
var accept = false;
foreach (var t in lambdas)
{
accept = accept || await t;
}
return(accept);
}
private async Task <bool> Run(char[] x, State p, int i, Stack <char> stack)
{
for (; i < x.Length; i++)
{
if (!Alphabet.Contains(x[i]))
{
return(false);
}
if (x[i] == Alphabet.EmptyString)
{
continue;
}
// Get possible transitions
var q = Transitions[p, x[i], stack.Peek()];
if (q.Length == 0) // nothing to do, stop
{
return(false);
}
if (q.Length == 1)
{
// try to update the stack. if we are out of bounds, reject
try { stack = updateStack(stack, q[0].Top, q[0].Replace); }
catch (Exception) { return(false); }
p = q[0].Q;
if (q[0].A == Alphabet.EmptyString)
{
i--; // Don't increment on null transition!
}
}
else
{
var tasks = new Task <bool> [q.Length];
// check each path asynchronously
for (var j = 0; j < q.Length; j++)
{
var s = new Stack <char>(stack);
try { s = updateStack(s, q[j].Top, q[j].Replace); }
catch (Exception) { continue; }
tasks[j] = Run(x, q[j].Q, q[j].A == Alphabet.EmptyString ? i : i + 1, s);
}
var result = false;
foreach (var t in tasks)
{
result = result || (t != null && await t);
}
return(result);
}
}
// No more moves!
if (p.Accepting)
{
return(true);
}
// check for lambda transitions
var r = Transitions[p, Alphabet.EmptyString, stack.Peek()];
var lambdas = new Task <bool> [r.Length];
for (var k = 0; k < r.Length; k++)
{
var s = new Stack <char>(stack);
try { s = updateStack(s, r[k].Top, r[k].Replace); }
catch (Exception) { continue; }
lambdas[k] = Run(x, r[k].Q, i, s);
}
var accept = false;
foreach (var t in lambdas)
{
accept = accept || (t != null && await t);
}
return(accept);
}
