常用语句 - C++

赋值

map

unordered_map<string, int> um1 = {{"apple", 1}, {"banana", 2}, {"orange", 3}};
// map 相同

结构体

struct GVAL {
    int t;    // 0=NULL, 1=int, 2=string
    int i;
    string s;
};
GVAL res1;
res0 = {0};
res1 = {1, 10};
res2 = {2, 0, "ok"};
-.OR.-
res2.t = 2;
res2.s = "ok";

// gcc version 9.4.0

数组

char buffer[msg_len + 1] = {0};          // 全部为 \0

memset(buffer, '\0', sizeof(buffer));    // 全部为 \0

P.S. char buffer[msg_len + 1] = {"a"}    // "a", \0, \0...

转换

数值转为字符串

#include <string>
str1 = to_string(num1);

字符串转换成整数

#include <string>
num1 = stoi(str1);

条件

map 元素是否存在

#include <map>
map<string, int> map1;
map1["key1"] = 123;
if (map1.count("key1")) {
    ...
}

循环

map

# C++11
for (const auto& pair1 : map1) {
    cout << pair1.first << ": " << pair1.second << endl;
}

# 基本方法：迭代器
for (map<int, string>::iterator it = map1.begin(); it != map1.end(); ++it) {
    cout << it->first << ": " << it->second << endl;
}

# 函数封装
#include <algorithm>
void printPair(const pair<int, string>& p) {
    cout << p.first << ": " << p.second << endl;
}
...
for_each(map1.begin(), map1.end(), printPair);

Compile

当前函数名

在大多数编译器中，__FUNCTION__ 宏会被替换为当前函数名

cout << "Current Function: " << __FUNCTION__ << endl;

• __FUNCTION__  : myfun
• __func__  : myfun
• __PRETTY_FUNCTION__ : void sys_info(string), gcc