Obscure C++ Features

[pingu]

WTF!!!

Obscure C++ Features - Made by Evan

 

[Daniel Duffy]

WTF!!!

Obscure C++ Features - Made by Evan

He's a show-off :D

Still, template template parameters are cool.

Some people get turned on by cryptic C++ syntax.

 

[Daniel Duffy]

I spent a Meetup C++evening in Amsterdam last month listening to this new obscure feature in C++17 You can program it in 5 minutes.

std::clamp - cppreference.com

The design is not even wrong :D

 

[Daniel Duffy]

    using A = std::decay<int>::type;         
    using B = std::decay<int&>::type;        
    using C = std::decay<int&&>::type;       
    using D = std::decay<const int&>::type;  
    using E = std::decay<int[2]>::type;      
    using F = std::decay<int (int)>::type;    

    using G = std::decay<volatile int>::type;         
    using H = std::decay<const volatile int&>::type;

 

[Liam]

These are all fairly basic and well-documented.
Not obscure RTFM :D

Most vexing parse
????

Agreed. The only C++ I regard as obscure is stuff I found in Mark Joshi's book on pricing patterns using stuff so obscure even STL experts find it obscure. Unsurprisingly I never used it in industry as it was all a bit too obscure.
Funky looking stuff but unless it's going to make an algorithm run 10x times faster I couldn't care less.

 

[ExSan]

C++ is not easy, it is not !

 

[Daniel Duffy]

C++ is not easy, it is not !

Did Jack Benny invent the joke “How do you get to Carnegie Hall?” whose punch line is “Practice, practice, practice”?

 

[Daniel Duffy]

Funky looking stuff but unless it's going to make an algorithm run 10x times faster I couldn't care less.

C++11/C++14 is shifting in the direction of compile-time polymorphism and away from subtype polymorphism to a) reduce code bloat b) improve performance over virtual functions c) catch bad designs and errors at compile-time.

 

[Daniel Duffy]

"Yes, seriously, C++17 brings std::variant. This is cool, and paves the way for future features building upon variant and other related ideas. Such as pattern matching, [...] std::variant is designed with the experience of boost::variant and other variant libraries."

 

[Daniel Duffy]

C++11 has this useful function

std::erf - cppreference.com

double CdfNormal(double x)
{ // aka N(x)

    const double sqrt2Inv = 1.0 / std::sqrt(2.0);
    return 0.5*(1.0 + std::erf(x * sqrt2Inv));
}

 

[Daniel Duffy]

int main()
    {
        [&]
        ()
        {}
        ;
        [=]
        ()
        {}
        ;
    }

 

[Daniel Duffy]

Why does this code not compile?

struct C
{
        C() = default;

        template <typename... Args>
            C(Args... args)
        {
       
        }
};

 

[Daniel Duffy]

Some C++11 to show the use of higher-order functions. Close to maths.
C++ is an extremely flexible language.

 

[Daniel Duffy]

 

[Daniel Duffy]

What's going on here?

    double S = 2.0; double K = 65.0; double h = 1.0;

    double sum = 0.0;
    for (int i = 1; i <= 100; ++i)
    {
        sum += std::sqrt(S / K); S -= h;
        std::cout << i << ",";
    }

    std::cout << std::boolalpha << "Sum: " << sum << '\n';