python (65.2k questions)

javascript (44.3k questions)

reactjs (22.7k questions)

java (20.8k questions)

c# (17.4k questions)

html (16.3k questions)

r (13.7k questions)

android (13k questions)

Questions - if-constexpr

C++ 17 What is the difference between a fold expression and if constexpr when using variadic template arguments (parameter pack)

I am trying to understand the difference between two approaches for handling parameter packs / variadic template arguments. There are two approaches mentioned in the linked article below. fold expres...
test-img

FreelanceConsultant

c++

c++17

variadic-templates

variadic-functions

if-constexpr

Votes: 0

Answers: 2

Latest Answer

First, this: template <class... Ts> void print_all(std::ostream& os, Ts const&... args) { ((os << args), ...); } is a template that will generate only one function per call li...
test-img

Fureeish

How can I static assert to disallow &quot;mixed endianness&quot; in a non-templated member function

I am using 2 x std::uint64_t and 1 x std::uint32_t in a high performance implementation of of operator<=> in a struct conataining a std::array<std::byte, 20>. I am trying to make it cross ...
test-img

Oliver Sch&#246;nrock

c++

endianness

static-assert

if-constexpr

Votes: 0

Answers: 2

Latest Answer

I suggest asserting that it's either big or little endian: #include <bit> #include <compare> struct pawned_pw { std::strong_ordering operator<=>(const pawned_pw& rhs) const ...
test-img

Ted Lyngmo

Is there a constexpr which lets me determine if there is an output operator (&lt;&lt;) for a particular type?

In order to prevent the compiler to apply e.g. a std::vector<T> to a statement like std::cout << u, I would like to do something like this: if constexpr (std::has_output_operator<U>)...
test-img

user1479670

c++

if-constexpr

Votes: 0

Answers: 1

Latest Answer

This can be done straightforwardly using the C++20 requires-expression, which checks whether its operand is valid: if constexpr (requires { std::cout << u; }) You can also define a named concep...
test-img

Brian Bi

SFINAE User-Defined-Conversion Operator

I'm trying to do a templated user-defined-conversion that uses design by introspection. In C++20 I can do the following: template<typename T> operator T() const { if constexp...
test-img

perryperry

c++

templates

sfinae

if-constexpr

c++

templates

sfinae

if-constexpr

Votes: 0

Answers: 1

Latest Answer

Can I do effectively what I can do with concepts with just SFINAE in C++17 for the user defined conversion operator? Consider that C++17 support if constepr. Given that you've developed a has_from_c...
test-img

max66

Posts

Questions

Blogs

Jobs