public static FA Optional(FA expr, int accept = -1)
{
var result = expr.Clone();
var f = result.FirstAcceptingState;
f.AcceptSymbol = accept;
result.EpsilonTransitions.Add(f);
return(result);
}
public static FA Concat(IEnumerable <FA> exprs, int accept = -1)
{
FA result = null, left = null, right = null;
foreach (var val in exprs)
{
if (null == val)
{
continue;
}
//Debug.Assert(null != val.FirstAcceptingState);
var nval = val.Clone();
//Debug.Assert(null != nval.FirstAcceptingState);
if (null == left)
{
if (null == result)
{
result = nval;
}
left = nval;
//Debug.Assert(null != left.FirstAcceptingState);
continue;
}
if (null == right)
{
right = nval;
}
//Debug.Assert(null != left.FirstAcceptingState);
nval = right.Clone();
_Concat(left, nval);
right = null;
left = nval;
//Debug.Assert(null != left.FirstAcceptingState);
}
if (null != right)
{
right.FirstAcceptingState.AcceptSymbol = accept;
}
else
{
result.FirstAcceptingState.AcceptSymbol = accept;
}
return(result);
}
public static FA Repeat(FA expr, int minOccurs = -1, int maxOccurs = -1, int accept = -1)
{
expr = expr.Clone();
if (minOccurs > 0 && maxOccurs > 0 && minOccurs > maxOccurs)
{
throw new ArgumentOutOfRangeException(nameof(maxOccurs));
}
FA result;
switch (minOccurs)
{
case -1:
case 0:
switch (maxOccurs)
{
case -1:
case 0:
return(Repeat(Optional(expr, accept), 1, 0, accept));
/*result = new FA();
* var final = new FA(true, accept);
* final.EpsilonTransitions.Add(result);
* foreach (var afa in expr.FillAcceptingStates())
* {
* afa.IsAccepting = false;
* afa.EpsilonTransitions.Add(final);
* }
* result.EpsilonTransitions.Add(expr);
* result.EpsilonTransitions.Add(final);
* //Debug.Assert(null != result.FirstAcceptingState);
* return result;*/
case 1:
result = Optional(expr, accept);
//Debug.Assert(null != result.FirstAcceptingState);
return(result);
default:
var l = new List <FA>();
expr = Optional(expr);
l.Add(expr);
for (int i = 1; i < maxOccurs; ++i)
{
l.Add(expr.Clone());
}
result = Concat(l, accept);
//Debug.Assert(null != result.FirstAcceptingState);
return(result);
}
case 1:
switch (maxOccurs)
{
case -1:
case 0:
result = new FA();
var final = new FA(true, accept);
final.EpsilonTransitions.Add(result);
foreach (var afa in expr.FillAcceptingStates())
{
afa.IsAccepting = false;
afa.EpsilonTransitions.Add(final);
}
result.EpsilonTransitions.Add(expr);
//Debug.Assert(null != result.FirstAcceptingState);
return(result);
case 1:
//Debug.Assert(null != expr.FirstAcceptingState);
return(expr);
default:
result = Concat(new FA[] { expr, Repeat(expr.Clone(), 0, maxOccurs - 1) }, accept);
//Debug.Assert(null != result.FirstAcceptingState);
return(result);
}
default:
switch (maxOccurs)
{
case -1:
case 0:
result = Concat(new FA[] { Repeat(expr, minOccurs, minOccurs, accept), Repeat(expr, 0, 0, accept) }, accept);
//Debug.Assert(null != result.FirstAcceptingState);
return(result);
case 1:
throw new ArgumentOutOfRangeException(nameof(maxOccurs));
default:
if (minOccurs == maxOccurs)
{
var l = new List <FA>();
l.Add(expr);
//Debug.Assert(null != expr.FirstAcceptingState);
for (int i = 1; i < minOccurs; ++i)
{
var e = expr.Clone();
//Debug.Assert(null != e.FirstAcceptingState);
l.Add(e);
}
result = Concat(l, accept);
//Debug.Assert(null != result.FirstAcceptingState);
return(result);
}
result = Concat(new FA[] { Repeat(expr.Clone(), minOccurs, minOccurs, accept), Repeat(Optional(expr.Clone()), maxOccurs - minOccurs, maxOccurs - minOccurs, accept) }, accept);
//Debug.Assert(null != result.FirstAcceptingState);
return(result);
}
}
// should never get here
throw new NotImplementedException();
}