article

• Did you know that C++20 extends support for data time utilities?

This time related support should be date library Implementation of. This has been promoting the standard. I don't know how it is going

constexpr auto thanksgiving = November / 25 / 2021y;

static_assert(year(2021) == thanksgiving.year());
static_assert(month(11)  == thanksgiving.month());
static_assert(day(25)    == thanksgiving.day());

• Correctly use TSC provided by cpu

You can get a faster speed than gettimeofday, but rdtsc also has a price. Here's a little popular science

• A footnote on "Three reasons to pass std::string_view by value"

As mentioned earlier, try to use string_view instead of const string_view & in addition, there is no difference in msvc. The reason for the implementation of msvc

• Designated Initializers in C++20

Is the initialization of the structure of c

struct Point { 
    double x { 0.0 };
    double y { 0.0 };
};

const Point p { .x = 10.0, .y = 20.0 };
 
const Point offset { .x { 100.0 }, .y { -100.0 } };

// mix also possible:
const Point translation { .x = 50.0, .y { -40.0 } };

• Underseeding mt19937; introducing xoshiro256ss

mt19937 is too slow to implement Xoshiro256ss replace

• Conditional Members

This paper introduces how to deal with these scenarios in c++20

How to make members generate [[no_unique_address]] + STD:: conditional according to conditions_ t

How to make member functions generate / restrict concept according to conditions

How to make types in a class generate / restrict inheritance STD:: conditional based on conditions_ t

• What if I told you, you don't have to run your unit tests ?

Simple interfaces are combined with compile time tests, constexpr as much as possible, and then static directly_ Assert test

#include <vector>
#include <string_view>
#include <numeric>

// std::isdigit is not constexpr
constexpr bool is_digit(char c)
{
    return c >= '0' && c <= '9';
}

constexpr unsigned int accumulate_string_digits(std::string_view str)
{
    std::vector<unsigned int> digits;
    for (auto c: str)
    {
        if (is_digit(c))
            digits.push_back(c - 48);
    }
    return std::accumulate(digits.begin(), digits.end(), 0);
}
static_assert(accumulate_string_digits("") == 0);
static_assert(accumulate_string_digits("1") == 1);
static_assert(accumulate_string_digits("12345") == 15);
static_assert(accumulate_string_digits("1a23c45c") == 15);
static_assert(accumulate_string_digits("Hello, World!") == 0);

• Constructors and evil initializers in C++

Discuss the abnormal security of the constructor, such as construction errors. The solution is to split the constructor. Remove init and execute it separately, but init may be omitted

Finally, the appropriate solution is to hide the constructor and use create instead of construct generation

class Rectangle {
    // ...

    Rectangle(int w, int h) : width(w), height(h), area(w * h) {
        assert(width > 0 && height > 0);
    }

public:
    static std::optional<Rectangle> create(int w, int h) {
        if (w <= 0 || h <= 0) {
            return std::nullopt;
        }
        return Rectangle(w, h);
    }

    // ...
};

video

• Jeff Garland - C++23 Standard Library Preview - Meeting C++ 2021

Introduce some small features of c++23

string

• string supports the contains method
• string constructed from nullptr will directly report an error

Module the pronunciation of module is mom's table. I always pronounce it as Ma Dou

• Some speed increases

io support

• std::print kills iostream, which is three times faster than printf
• Some runtime matching errors in std::format are transferred to the compile time for judgment. / / this is also mentioned in cppcon 2021 and has not been released yet

A bunch of fix and new interfaces in range, and range is more functional

Constexpr various, such as unique_ PTR, cmath interface, optional, etc. memory allocation can even be constexpr

miscellaneous

• Monadic option makes it easier to use, and_ These little interfaces
• std::expected is a classic one, in the form of the status class of rocksdb
• Which library should stacktrace boost
• byteswap is introduced after std::endian
• to_underlying gets the value behind the enumeration. You don't need to cast. The standard library tool helps you cast

project

• Oof (omnipotent output friend) A terminal graphics library
• shadesmar Fast C++ IPC using shared memory can also be used this
• cmake-init A minimal cmake template
• Add GitHub Ci to CRC Library https://github.com/stbrumme/crc32/pull/11
• cutlass CUDA matrix calculation library