public IEnumerator <Node> GetNodes(int cutAt)
{
if (cutAt < 0)
{
yield return(null);
}
if (cutAt >= expr.Count)
{
yield return(null);
}
CatExpr leftSubExpr = expr.GetRangeFromTo(0, cutAt);
CatExpr rightSubExpr = expr.GetRangeFromTo(cutAt + 1, expr.Count - 1);
Node leftNode = MakeNode(leftSubExpr);
Node rightNode = MakeNode(rightSubExpr);
foreach (Node node in leftNode.GetNodeIter())
{
yield return(Compose(leftNode, node));
}
foreach (Node node in rightNode.GetNodeIter())
{
yield return(Compose(node, rightNode));
}
}
static public MacroMatch Create(AstMacro m, CatExpr fxns, int nPrevMatchPos, int nFxnIndex, int nSubExprSize)
{
if (nFxnIndex < 0)
{
return(null);
}
if (nFxnIndex >= fxns.Count)
{
return(null);
}
List <AstMacroTerm> pattern = m.mSrc.mPattern;
MacroMatch match = new MacroMatch(m);
int nFirst = nFxnIndex;
int nLast = nFxnIndex;
int nTokenIndex = pattern.Count - 1;
// Start at the end of the pattern and move backwards comparing expressions
while (nFirst > nPrevMatchPos)
{
Trace.Assert(nTokenIndex <= pattern.Count);
Trace.Assert(nFirst >= 0);
Trace.Assert(nLast >= nFirst);
Trace.Assert(nTokenIndex < pattern.Count);
// get the current sub-expression that we are evaluating
CatExpr expr = fxns.GetRangeFromTo(nFirst, nLast);
AstMacroTerm tkn = pattern[nTokenIndex];
bool bRecoverable = false;
if (match.DoesTokenMatch(tkn, expr, out bRecoverable))
{
// Check if we have matched the whole pattern
if (nTokenIndex == 0)
{
match.mnFxnIndex = nFirst;
match.mnFxnCount = (nFxnIndex - nFirst) + 1;
return(match);
}
// Go to the previous token
nTokenIndex -= 1;
// Adjust the sub-expression range
nFirst -= 1;
nLast = nFirst;
}
else
{
// Some failed matches (such as identifier names) can not be recovered from.
if (!bRecoverable)
{
return(null);
}
// Widen the sub-expression.
nFirst -= 1;
// Check if we have passed the limit of how big of a
// sub-expression will be examined
if (nLast - nFirst > nSubExprSize)
{
return(null);
}
}
}
// The loop was finished and no match was found.
return(null);
}