错误:使用已删除功能

error: use of deleted function?

本文关键字：删除 功能 错误      更新时间：2023-10-16

我当前正在尝试实现一个简单的btree，但似乎在这里遇到了一个问题。

#include <iostream>
#include <cstdlib>
#include <vector>
#include <algorithm>
struct element
{
    int x;
    int y;
    element (int x, int y)
    {
        this->x = x;
        this->y = y;
    }
};
int sum(element key)
{
    return key.x + key.y;
}
struct node
{
    element key;
    node *child_left;
    node *child_right;
};

class tree{
    void insert(element key);
    void insert(element key, node* leaf);
    node* root;
    tree()
    {
        this->root = NULL;
    }
};
void tree::insert(element key){
    if(this->root != NULL){
        insert(key, this->root);
    }else{
        this->root = new node;
        this->root->key.x = key.x;
        this->root->key.y = key.y;
        this->root->child_left = NULL;
        this->root->child_right = NULL;

    }
}

void tree::insert(element key, node* leaf){
    if(sum(key) < sum(leaf->key)){
        if(leaf->child_left != NULL){
            insert(key, leaf->child_left);
        }else{
          leaf->child_left = new node;
          leaf->child_left->key.x = key.x;
          leaf->child_left->key.y = key.y;
          leaf->child_left->child_left = NULL;
          leaf->child_left->child_right = NULL;
        }
    }else if(sum(key) >= sum(leaf->key)){
        if(leaf->child_right != NULL){
            insert(key, leaf->child_right);
        }else{
            leaf->child_right = new node;
            leaf->child_right->key.x = key.x;
            leaf->child_right->key.y = key.y;
            leaf->child_right->child_left = NULL;
            leaf->child_right->child_right = NULL;
        }
    }
}
int main()
{
    std::cout << "Somet"<< std::endl;
}

https://wandbox.org/permlink/0inxxblt59pfvppt

给我错误消息：

Start
prog.cc: In member function 'void tree::insert(element)':
prog.cc:49:20: error: use of deleted function 'node::node()'
   this->root = new node;
                    ^~~~
prog.cc:26:8: note: 'node::node()' is implicitly deleted because the default definition would be ill-formed:
 struct node
        ^~~~
prog.cc:26:8: error: no matching function for call to 'element::element()'
prog.cc:14:5: note: candidate: 'element::element(int, int)'
     element (int x, int y)
     ^~~~~~~
prog.cc:14:5: note:   candidate expects 2 arguments, 0 provided
prog.cc:10:8: note: candidate: 'constexpr element::element(const element&)'
 struct element
        ^~~~~~~
prog.cc:10:8: note:   candidate expects 1 argument, 0 provided
prog.cc:10:8: note: candidate: 'constexpr element::element(element&&)'
prog.cc:10:8: note:   candidate expects 1 argument, 0 provided
prog.cc: In member function 'void tree::insert(element, node*)':
prog.cc:66:28: error: use of deleted function 'node::node()'
     leaf->child_left = new node;
                            ^~~~
prog.cc:76:28: error: use of deleted function 'node::node()'
    leaf->child_right = new node;
                            ^~~~
1
Finish

我不确定我明白为什么这会引起问题……因此，某些解释会被赞赏，结构（和类）本身是否具有默认的构造函数？那为什么要抱怨呢？

删除了 node的默认构造函数，因为 element却没有（这是btw恰好是错误消息试图告诉您的;）。element没有编译器生成的默认构造函数，因为您提供了自己的构造函数（这不是默认的构造函数，即没有参数就无法称呼它）。要么为node编写将参数传递给element构造函数的默认构造函数：

node() : key(element(1,2)) {}

或一个用于element：

element(int x=0,int y=0) : x(x),y(y) {}

在后一种情况下，node的默认构造函数可以并且将由编译器生成，因为这实际上只是这样：

node() {}
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