最后,从这个问题出发,问题仍然存在,即该子解析器...
private static void Factor(Scanner scanner, ref TermNode currentTree, ref Token currentToken)
{
Exponent(scanner, ref currentTree, ref currentToken);
while (currentToken is OperatorToken && ((OperatorToken)currentToken).OperatorChar == '^') // So long as the token is ^
{
TermNode node = new TermNode(currentTree, null, currentToken);
currentTree = null;
scanner.MoveNext();
currentToken = scanner.Current;
Exponent(scanner, ref currentTree, ref currentToken);
node.RightChild = currentTree;
currentTree = node;
}
}
...不正确地处理指数运算符(“^”)。这是因为它是右结合的。上面的代码处理它就好像它是左关联的。
例如:文本e^x^2
被解释为(e^x)^2
。然而,正确的“解释”应该是e^(x^2)
。
我已经尝试过类似于以下内容:
if (/* The current token is ^ */)
{
TermNode node = new TermNode(tree, null, currentToken);
tree = null;
scanner.MoveNext();
currentToken = scanner.Current;
Exponent(ref tree);
node.RightChild = tree;
tree = node;
}
while (/* The current token is ^ */)
{
TermNode detachedExponent = tree.RightChild;
TermNode oldTree = tree;
Token token = currentToken;
tree.RightChild = null;
tree = null;
scanner.MoveNext();
currentToken = scanner.Current;
Exponent(ref tree);
oldTree.RightChild = new TermNode(distachedExponent, tree, token);
tree = oldTree;
}
这只适用于两个连续的"^"表达式。而不是像e^x^y^z
这样的表达式(它应该是e^(x^(y^z))
而不是像解析器所声明的那样e^((x^y)^z)
)。我错过了什么?