[英]C2678: error on insertion of Binary search tree c++
Using visual studios 2015 for C++ implementation I am receiving a compilation error in my insertHelper()
. 使用Visual insertHelper()
2015 for C ++实现,我在insertHelper()
收到编译错误。
Insert Helper is a recursive function listed below. 插入帮助器是下面列出的递归函数。
template < typename DataType, typename KeyType >
void BSTree<DataType, KeyType>::insertHelper(BSTreeNode *&p,
const DataType &newDataItem)
// Recursive helper function for insert. Inserts newDataItem in
// the subtree pointed to by p.
{
if (p == NULL) {
p->dataItem = newDataItem;
p->left = NULL;
p->right = NULL;
}
else {
if (p->dataItem < newDataItem) { // <- error triggers here
insertHelper(p->left, newDataItem);
}
else {
insertHelper(p->right, newDataItem);
}
}
}
Insert Helper is called by insert here: Insert Helper在这里通过insert调用:
template < typename DataType, typename KeyType >
void BSTree<DataType, KeyType>::insert(const DataType &newDataItem)
// Inserts newDataItem into a tree. If an data item with the same key
// as newDataItem already exists in the tree, then updates that
// data item's data with newDataItem's data.
{
insertHelper(root, newDataItem);
}
And a simplified version of my trees header file is here. 我的树头文件的简化版本在这里。
#ifndef BSTREE_H
#define BSTREE_H
#include <stdexcept>
#include <iostream>
using namespace std;
template < typename DataType, class KeyType > // DataType : tree data item
class BSTree // KeyType : key field
{
public:
// Constructor
BSTree(); // Default constructor
// Binary search tree manipulation operations
void insert(const DataType& newDataItem); // Insert data item
protected:
class BSTreeNode // Inner class: facilitator for the BSTree class
{
public:
// Constructor
BSTreeNode(const DataType &nodeDataItem, BSTreeNode *leftPtr, BSTreeNode *rightPtr);
// Data members
DataType dataItem; // Binary search tree data item
BSTreeNode *left, // Pointer to the left child
*right; // Pointer to the right child
};
// Recursive helpers for the public member functions -- insert
// prototypes of these functions here.
void insertHelper(BSTreeNode *&p, const DataType &newDataItem);
// Data member
BSTreeNode *root; // Pointer to the root node
};
#endif // define BSTREE_H
Test Data and initialization : 测试数据和初始化:
class TestData
{
public:
void setKey ( int newKey )
{ keyField = newKey; } // Set the key
int getKey () const
{ return keyField; } // Returns the key
private:
int keyField; // Key for the data item
};
int main()
{
BSTree<TestData,int> testTree; // Test binary search tree
TestData testData; // Binary search tree data item
}
I don't understand why I can't use if (p->dataItem < newDataItem){}
. 我不明白为什么我不能使用if (p->dataItem < newDataItem){}
。 I've tried if (p.dataItem < newDataItem){}
and even just if (dataItem < newDataItem){}
. 我已经尝试过if (p.dataItem < newDataItem){}
,甚至只是if (dataItem < newDataItem){}
。 And I am getting nowhere fast with this bug. 而且我没有很快解决这个错误。 Any help would be appreciated. 任何帮助,将不胜感激。
The error reads: 该错误显示为:
C2678 : binary '<': no operator found which takes a left-hand BST operand of type 'TestData' (or there is no acceptable conversion). C2678:二进制'<':未找到采用“ TestData”类型的左侧BST操作数的运算符(或没有可接受的转换)。
if (p->dataItem < newDataItem) { // <- error triggers here
base on 基于
BSTree<TestData,int> testTree;
we know that p->dataItem
and newDataItem
are of type TestData
. 我们知道p->dataItem
和newDataItem
的类型为TestData
。
So the comparison above expands to 所以上面的比较扩展到
if (p->dataItem.operator<(newDataItem))
Now lets look at the error message again: 现在,让我们再次查看错误消息:
binary '<': no operator found which takes a left-hand BST operand of type 'TestData' (or there is no acceptable conversion).
It was looking for a binary '<' operator. 它正在寻找二进制“ <”运算符。 You haven't provided one, so the language can't implement your requested <
comparison. 您尚未提供一个,因此该语言无法实现您请求的<
比较。
class TestData
{
public:
void setKey ( int newKey )
{ keyField = newKey; } // Set the key
int getKey () const
{ return keyField; } // Returns the key
bool operator < (const TestData& rhs) const
{ return keyField < rhs.keyField; }
private:
int keyField; // Key for the data item
};
or 要么
class TestData
{
public:
void setKey ( int newKey )
{ keyField = newKey; } // Set the key
int getKey () const
{ return keyField; } // Returns the key
friend bool operator < (const TestData&, const TestData&);
private:
int keyField; // Key for the data item
};
bool operator < (const TestData& lhs, const TestData& rhs)
{
return lhs.keyField < rhs.keyField;
}
Live demo: http://ideone.com/Y7JGCD 现场演示: http : //ideone.com/Y7JGCD
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