c_cpp 茴字的四种写法（C ++）

Posted 2021-05-14

//
//  returnArray.cpp
//  return array as reference.
//
//  Created by pezy on 14/10/30.
//  Copyright (c) 2014 pezy. All rights reserved.
//

#include <iostream>
#include <string>

using std::string; using std::cout; using std::endl;

using ArrT = string[10];

ArrT& func1(ArrT& arr)
{
    arr[0] = "pezy@1";
    arr[1] = "mooophy@1";
    arr[2] = "quee@1";
    
    return arr;
}

auto func2(ArrT& arr) -> string(&)[10]
{
    arr[0] = "pezy@2";
    arr[1] = "mooophy@2";
    arr[2] = "quee@2";
    
    return arr;
}

string arrS[10];
decltype(arrS)& func3(ArrT& arr)
{
    arr[0] = "pezy@3";
    arr[1] = "mooophy@3";
    arr[2] = "quee@3";
    
    return arr;
}

string (&func(string (&arrStr)[10]))[10]
{
    arrStr[0] = "pezy";
    arrStr[1] = "mooophy";
    arrStr[2] = "quee";
    return arrStr;
}

int main(int argc, const char * argv[]) {
    
    string arrStr[10];
    for (const auto& str : func(arrStr))
        if (!str.empty())
            cout << str << endl;
    
    return 0;
}

#include <iostream>

using std::cout; using std::endl; using std::begin; using std::end;

int main()
{
  constexpr size_t rowCnt = 3, colCnt = 4;
  int ia[rowCnt][colCnt];
  
  // subscirpting
  for (size_t i = 0; i != rowCnt; ++i)
    for (size_t j = 0; j != colCnt; ++j)
      ia[i][j] = i*colCnt + j;
  
  // range for
  size_t cnt = 0;
  for (auto &row : ia)
    for (auto &col : row)
      col = cnt++;
  
  // output (use range for)
  for (const auto& row : ia)
    for (auto col : row)
      cout << col << " ";
  cout << endl;
  
  // output (use pointers)
  for (auto p = begin(ia); p != end(ia); ++p)
    for (auto q = begin(*p); q != end(*p); ++q)
      cout << *q << " ";
  cout << endl;
  
  // output (use type aliases)
  using int_array = int[4];
  for (int_array *p = ia; p != ia + 3; ++p)
    for (int *q = *p; q != *p + 4; ++q)
      cout << *q << " ";
  cout << endl;
  
  return 0;
}