/// <inheritdoc />
protected override GrammarNode <Char>?VisitStringTerminal(StringTerminal stringTerminal, OptimizeArgs argument)
{
if (stringTerminal.Value.Length == 1)
{
return(new CharacterTerminal(stringTerminal.Value[0]));
}
else
{
return(stringTerminal);
}
}
/// <summary> /// Folds a string terminal node. /// </summary> /// <param name="characterTerminalString"></param> /// <param name="argument">The argument to be passed to the visitor method.</param> /// <returns> /// <list type="number"> /// <item>The original node if it's to be kept</item> /// <item>A different node to replace the original node with</item> /// <item>Null if the node is to be removed</item> /// </list> /// </returns> protected override GrammarNode <Char>?VisitStringTerminal(StringTerminal characterTerminalString, TArgument argument) => characterTerminalString;
protected override String?VisitStringTerminal(StringTerminal stringTerminal, Unit argument) => stringTerminal.Value;
/// <inheritdoc />
protected override GrammarNode <Char>?VisitSequence(Sequence <Char> sequence, OptimizeArgs argument)
{
var nodes = sequence.GrammarNodes.Select(node => this.Visit(node, argument))
.Where(node => node is not null)
.ToList();
for (var nodeIdx = 0; nodeIdx < nodes.Count; nodeIdx++)
{
loopStart:
GrammarNode <Char> currentNode = nodes[nodeIdx] !;
if (nodeIdx < nodes.Count - 1)
{
GrammarNode <Char> nextNode = nodes[nodeIdx + 1] !;
if (currentNode is CharacterTerminal currentCharacterTerminal)
{
if (nextNode is CharacterTerminal nextCharacterTerminal)
{
nodes.RemoveAt(nodeIdx);
nodes[nodeIdx] = new StringTerminal(new String(new[] { currentCharacterTerminal.Value, nextCharacterTerminal.Value }));
goto loopStart;
}
else if (nextNode is StringTerminal nextStringTerminal)
{
nodes.RemoveAt(nodeIdx);
nodes[nodeIdx] = new StringTerminal(currentCharacterTerminal.Value + nextStringTerminal.Value);
goto loopStart;
}
}
else if (currentNode is StringTerminal currentStringTerminal)
{
if (nextNode is CharacterTerminal nextCharacterTerminal)
{
nodes.RemoveAt(nodeIdx);
nodes[nodeIdx] = new StringTerminal(currentStringTerminal.Value + nextCharacterTerminal.Value);
goto loopStart;
}
else if (nextNode is StringTerminal nextStringTerminal)
{
nodes.RemoveAt(nodeIdx);
nodes[nodeIdx] = new StringTerminal(currentStringTerminal.Value + nextStringTerminal.Value);
goto loopStart;
}
}
}
}
if (nodes.Count == 0)
{
return(null);
}
else if (nodes.Count == 1)
{
return(nodes[0]);
}
else if (nodes.SequenceEqual(sequence.GrammarNodes))
{
return(sequence);
}
else
{
return(new Sequence <Char>(nodes !));
}
}
/// <summary> /// Visits a string terminal. /// </summary> /// <param name="characterTerminalString"></param> /// <param name="argument">The argument data passed by the caller.</param> /// <returns>The result of visiting this node.</returns> protected abstract TReturn VisitStringTerminal(StringTerminal characterTerminalString, TArgument argument);
