c++ 知识点（不断更新）-白红宇

c++ 知识点（不断更新）

阅读量：4210 次

发布时间：2019-05-26

本文共 2770 字，大约阅读时间需要 9 分钟。

1 .指针赋值

typedef tree_node
   
     node_type;node_type* root;node_type **n =&root; //这里root虽然是个指针但是可能是空值,为了给指针赋值，所以取地址*n =new node_type(v,p,0,0);

2 . c++ callback 函数

Using StatusCallback = std::function
   
    
     >使用template构造函数：// A generic for loop on GPUtemplate 
     
      __global__void loop_kernel(        SizeT loop_size,        OpT   op){    const SizeT STRIDE = (SizeT)gridDim.x * blockDim.x;    SizeT i = (SizeT)blockDim.x * blockIdx.x + threadIdx.x;    while (i < loop_size) {        op(i);        i += STRIDE;    }}

3 . 其中shared_ptr 指针初始化类似上面的：

template 
   
    Status TorchOpContext
    
     ::AllocatePersistent(    int64_t size, std::shared_ptr
     
      * tensor) {  // Allocation errors are handled using PyTorch exceptions.  *tensor = std::make_shared
      
       (device_, size);  return Status::OK();}

4 . pair类型vector

std::vector
   
    
     > layers;layers.push_back(std::make_pair(1,1));

5 . tuple类型vector

std::vector
   
    
      > chunks;chunks.push_back(std::make_tuple(  chunk_start, chunk_size, chunk_offset_bytes));SizeT chunk_start = std::get<0>(chunk);SizeT chunk_size  = std::get<1>(chunk);size_t chunk_offset = std::get<2>(chunk);

6 . explict 关键字：禁止隐式构造函数

7 . typedef double(*func)();

8 . realloc : 动态内存分配

9 . c++ lambda 函数：

语法定义：[capture](parameters) mutable -> return-type{ statements }

10 . reinterpret_cast

unsigned int key_bits   = *reinterpret_cast
   
    (const_cast
    
     (&key));

11 . operation 相关重载函数

Operator: 相关的重载函数1. std::ostream & operator <<(std::ostream & out ,const half_t &x){             out<<(float)x;              return out;}     2. bool operator >=(const half_t & other) const{                return float(*this) >= float(other);}3. half_t & operator +=(const half_t &rhs){                *this =half_t(float(*this)+float(rhs));                reuturn &=*this;}4. operator float() const{                uint32_t f =0;                return *reinterpret_cast
   
    (&f);}5. operator __half()const{            Return reinterpret_cast
    
     (__x);}6. ++ 重载self_type &operator++(){    if(pos){        //首先确保不是空的迭代器，再查看有没有右子树        if(pos->right){            //定位到右子树的最左节点            pos=pos->right;            while (pos->left)pos=pos->left;        }else{            //定位到尚未访问过的祖先节点            while ((pos->parent)&&(pos->parent->right==pos))pos=pos->parent;            pos=pos->parent;        }    }    return *this;}7. 指针重载reference_type & operator *()const throw(std::runtime_error){    if(pos)return pos->value;    else {        throw  std::runtime_error("dereference null iterator!");    }}8. !=  重载template 
     
      bool operator !=(tree_iterator
      
       const & left,tree_iterator
       
         const & right){    return !(left==right);}