[[nodiscard]] is a property introduced in C 17 to prompt the compiler to warn the situation where the function returns value is ignored. 1. Commonly used functions to return error codes, states or resource handles; 2. Can act on function declarations, return types, enums or classes; 3. Use (void) to explicitly ignore the return value; 4. Mainstream compilers support but do not forcefully block compilation; 5. It is recommended to use key return values to affect program logic to avoid abuse.

std::cout is an object in C used to output data to the console and belongs to the standard library. It passes

The key steps to install PHP on Windows include: 1. Download the appropriate PHP version and decompress it. It is recommended to use ThreadSafe version with Apache or NonThreadSafe version with Nginx; 2. Configure the php.ini file and rename php.ini-development or php.ini-production to php.ini; 3. Add the PHP path to the system environment variable Path for command line use; 4. Test whether PHP is installed successfully, execute php-v through the command line and run the built-in server to test the parsing capabilities; 5. If you use Apache, you need to configure P in httpd.conf

The key to C performance optimization is to understand language features, compiler behavior, and hardware interaction. 1. Use inline functions and const references reasonably, use inline only for small and frequently called functions, and use const& to avoid copy overhead of custom types. 2. Avoid unnecessary memory allocation, reduce the number of memory re-allocations in the container through reserve(), or reuse memory using a memory pool. 3. Design cache-friendly data structures, keep data compact, give priority to continuous memory storage, and consider structure splitting to improve cache hit rate. 4. Make full use of compiler optimization options, such as -O2/-O3, -march=native and -flto, but the volume and

The easiest way to get user input in C is to use std::cin. 1. When reading a single value, you can use std::cin>>variable, suitable for integers or strings without spaces; 2. To read the entire line content containing spaces, you should use std::getline(std::cin,stringVariable); 3. If you call std::getline() after std::cin>>, you need to add std::cin.ignore() to clear the newline; 4. If the type does not match during input verification, std::cin will enter a failed state, and you can use std::cin.clear

Reading JSON files can be implemented in Python through the json module. The specific steps are: use the open() function to open the file, use json.load() to load the content, and the data will be returned in a dictionary or list form; if you process JSON strings, you should use json.loads(). Common problems include file path errors, incorrect JSON format, encoding problems and data type conversion differences. Pay attention to path accuracy, format legality, encoding settings, and mapping of boolean values and null.

In C, memory management requires manual operations or the object life cycle to manage resources. The core methods include: 1. Use new and delete to manually manage memory, and pay attention to avoid memory leakage, hanging pointers and repeated releases; 2. Follow the RAII principle, obtain resources through constructors and automatically release destructors to ensure exception security and concise code; 3. Use smart pointers unique_ptr and shared_ptr to improve security to avoid manual release problems, but beware of shared_ptr's circular reference. Mastering these mechanisms can effectively improve the efficiency and stability of the program.

In Python, using a for loop with the range() function is a common way to control the number of loops. 1. Use when you know the number of loops or need to access elements by index; 2. Range(stop) from 0 to stop-1, range(start,stop) from start to stop-1, range(start,stop) adds step size; 3. Note that range does not contain the end value, and returns iterable objects instead of lists in Python 3; 4. You can convert to a list through list(range()), and use negative step size in reverse order.