private void ConvertNodeConcatenate(RegexNode node)
{
var children = node._children;
if (children.Count == 1)
ConvertNode(children[0]);
else
{
for (int i = 0; i < children.Count; i++)
{
if (i < children.Count-1)
Write("(re-concat ");
else
Write(" ");
ConvertNode(children[i]);
}
for (int i = 0; i < children.Count - 1; i++)
Write(")");
}
}