public static Match PartialSecond(BooleanExpression _c, SymbolicString remaining2)
{
return(new Match(
_c,
SymbolicString.Epsilon(),
remaining2
));
}
public static Match PartialFirst(BooleanExpression _c, SymbolicString remaining1)
{
return(new Match(
_c,
remaining1,
SymbolicString.Epsilon()
));
}
public static Match FullMatch(BooleanExpression _c)
{
return(new Match(
_c,
SymbolicString.Epsilon(),
SymbolicString.Epsilon()
));
}
private static IEnumerable <Match> matchSymbolConcat(SymbolicString s1, SymbolicString s2)
{
if (s2.isEpsilon())
{
yield return(Match.PartialFirst(LogicalExpression.True(), s1));
yield break;
}
var rest = SymbolicString.Concat(s2.sub_strings.Skip(1));
foreach (var m in match(s1, s2.sub_strings.First()))
{
foreach (var mp in m.continueMatch(SymbolicString.Epsilon(), rest))
{
yield return(mp);
}
}
}
private static IEnumerable <Match> matchRepeatConcat(SymbolicString s1, SymbolicString s2)
{
if (s2.isEpsilon())
{
yield return(Match.FullMatch(ComparisonExpression.Equal(s1.length(), 0)));
yield return(Match.PartialFirst(ComparisonExpression.GreaterThan(s1.length(), 0), s1));
yield break;
}
var first = s2.sub_strings.First();
var rest = SymbolicString.Concat(s2.sub_strings.Skip(1));
foreach (var m in match(s1, first))
{
foreach (var mp in m.continueMatch(SymbolicString.Epsilon(), rest))
{
yield return(mp);
}
}
}
// Generate TwoSplit's where either one may be empty
// Generates the splits in order, i.e., by length of the prefix
// So, for s being symbol and concat, first one will always be (\epsilon, s) and last one always (s, \epsilon)
// So, for s being repeat (abc)^n, first will be ((abc)^i,(abc)^j) and last one always ((abc)^i ab, c(abc)^j)
// Requires a flat symbolic string
public IEnumerable <TwoSplit> TwoSplits()
{
SymbolicString prefix, suffix;
// Contract.Requires(this.isFlat());
switch (this.expression_type)
{
case SymbolicStringType.Symbol:
yield return(TwoSplit.MakeSplit(SymbolicString.Epsilon(), this, LogicalExpression.True()));
yield return(TwoSplit.MakeSplit(this, SymbolicString.Epsilon(), LogicalExpression.True()));
break;
case SymbolicStringType.Concat:
yield return(TwoSplit.MakeSplit(SymbolicString.Epsilon(), this, LogicalExpression.True()));
for (int i = 0; i < this.sub_strings.Count; i++)
{
prefix = SymbolicString.Concat(this.sub_strings.Take(i).ToList());
suffix = SymbolicString.Concat(this.sub_strings.Skip(i + 1).ToList());
foreach (var split in this.sub_strings[i].TwoSplits())
{
if (!split.start.isEpsilon())
{
yield return(split.extend(prefix, suffix));
}
}
}
break;
case SymbolicStringType.Repeat:
var v1 = LinearIntegerExpression.FreshVariable();
var v2 = LinearIntegerExpression.FreshVariable();
var sanityConstraint = LogicalExpression.And(
ComparisonExpression.GreaterThanOrEqual(v1, 0),
ComparisonExpression.GreaterThanOrEqual(v2, 0)
);
prefix = SymbolicString.Repeat(this.root, v1);
suffix = SymbolicString.Repeat(this.root, v2);
yield return(TwoSplit.MakeSplit(
prefix,
suffix,
LogicalExpression.And(sanityConstraint, ComparisonExpression.Equal(v1 + v2, this.repeat))
));
if (this.root.expression_type != SymbolicStringType.Concat)
{
break;
}
for (int i = 1; i < this.root.sub_strings.Count; i++)
{
var split = TwoSplit.MakeSplit(
SymbolicString.Concat(this.root.sub_strings.Take(i)),
SymbolicString.Concat(this.root.sub_strings.Skip(i)),
LogicalExpression.And(
ComparisonExpression.Equal(v1 + v2 + 1, this.repeat),
sanityConstraint
)
);
yield return(split.extend(prefix, suffix));
}
break;
default:
throw new ArgumentOutOfRangeException();
}
}
// Generates splits where all three parts may be empty
public IEnumerable <Split> Splits()
{
// Contract.Requires<ArgumentException>(this.isFlat());
switch (this.expression_type)
{
case SymbolicStringType.Symbol:
yield return(Split.MakeSplit(this, SymbolicString.Epsilon(), SymbolicString.Epsilon(), LogicalExpression.True()));
yield return(Split.MakeSplit(SymbolicString.Epsilon(), this, SymbolicString.Epsilon(), LogicalExpression.True()));
yield return(Split.MakeSplit(SymbolicString.Epsilon(), SymbolicString.Epsilon(), this, LogicalExpression.True()));
break;
case SymbolicStringType.Repeat:
var v1 = LinearIntegerExpression.FreshVariable();
var v2 = LinearIntegerExpression.FreshVariable();
var v3 = LinearIntegerExpression.FreshVariable();
var sanityConstraint = LogicalExpression.And(
ComparisonExpression.GreaterThanOrEqual(v1, 0),
ComparisonExpression.GreaterThanOrEqual(v2, 0),
ComparisonExpression.GreaterThanOrEqual(v3, 0)
);
// Suppose the word w = a_0 a_1 \ldots a_{n-1}
// All splits are of the form
// BEG: (a_0 \ldots a_{n-1})^i (a_0 \ldots a_p) = w^i . w_1
// MID: (a_{p+1} \ldots a_{n-1} a_0 \ldots a_p)^j (a_{p+1} \ldots a_q) = (w_2 w_1)^j w_3
// END: (a_{q+1} \ldots a_{n-1}) (a_0 \ldots a_{n-1})^k = w_4 w^k
var w = this.root.wordSymbols();
var ww = w.Concat(w);
int n = w.Count();
for (int w1len = 0; w1len < n; w1len++)
{
var w_1 = w.Take(w1len);
var w_2 = w.Skip(w1len);
var beg = SymbolicString.Concat(
SymbolicString.Repeat(this.root, v1),
SymbolicString.Concat(w_1));
var mid_root = SymbolicString.Concat(
SymbolicString.Concat(w_2),
SymbolicString.Concat(w_1));
var mid_beg = SymbolicString.Repeat(mid_root, v2);
for (int w3len = 0; w3len < n; w3len++)
{
var w_3 = ww.Skip(w1len).Take(w3len);
var mid = SymbolicString.Concat(mid_beg, SymbolicString.Concat(w_3.ToList()));
IEnumerable <SymbolicString> w_4;
if (w1len + w3len == 0)
{
w_4 = new List <SymbolicString>();
}
else if (w1len + w3len <= n)
{
w_4 = w.Skip(w1len).Skip(w3len);
}
else
{
w_4 = ww.Skip(w1len).Skip(w3len);
}
var end = SymbolicString.Concat(
SymbolicString.Concat(w_4.ToList()),
SymbolicString.Repeat(this.root, v3)
);
var consumed = (w_1.Count() + w_3.Count() + w_4.Count()) / w.Count();
yield return(Split.MakeSplit(
beg,
mid,
end,
LogicalExpression.And(
ComparisonExpression.Equal(v1 + v2 + v3 + consumed, this.repeat),
sanityConstraint
)
));
}
}
break;
case SymbolicStringType.Concat:
foreach (var beg_midend in this.TwoSplits())
{
foreach (var mid_end in beg_midend.end.TwoSplits())
{
yield return(Split.MakeSplit(
beg_midend.start,
mid_end.start,
mid_end.end,
LogicalExpression.And(beg_midend.constraints, mid_end.constraints)));
}
}
break;
default:
throw new ArgumentOutOfRangeException();
}
}