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Questions tagged [variadic-templates]

Variadic templates are templates that take a variable number of parameters.

Some programming languages, like D and C++ since with the C++11 standard, support templates that take a variable number of parameters. Variadic templates are useful in a number of situations, for example, defining type-safe heterogeneous containers such as tuples and expanded metaprogramming library facilities.

http://en.wikipedia.org/wiki/Variadic_templates

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C++ function call wrapper with function as template argument

I'm trying to create a generic wrapper function that takes a function as a template argument and takes the same arguments as that function as its arguments. For example: template /* return type of F */ wrapper(Ts... Args /* not…
Eric
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Are variadic arguments after a defaulted parameter well-formed?

template void bark( int = 0, Args&&... args ) {} int main() { bark(); bark(1); bark(1, 2); } Is this code well-formed according to the C++ Standard? The proposed duplicate does not contain the same calls of the…
Puppy
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How can I expand call to variadic template base classes?

I have a set of non-orthogonal policies, all of them implementing a common named method, the policies add safety checks. I want users to be able to combine the policies to allow more complex validation without creating policies for each combination…
dvicino
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Checking type of parameter pack using enable_if

Since there is a restriction on allowed non-type variadic templates, I am trying to write a function taking an arbitrary number of doubles using enable_if. In essence, I want to do something like: template
user1997744
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Wrap a function pointer in C++ with variadic template

The Question I have a number of C++ functions void f(), R g(T a), S h(U a, V b) and so on. I want to write a template function that accepts f, g, h and so on as a template argument and calls that function. ie I want something like…
0xbe5077ed
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Unpacking parameter packs in template aliases

I run into a problem with unpacking variadic templates into a template alias. The following code works with Clang 3.4 and GCC 4.8 but fails with GCC 4.9: template using front_type = T; template struct…
mavam
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isn't non-type parameter pack that evaluates to "void..." illegal?

gcc-4.8 accepts this code, but isn't it wrong since the non-type parameter pack is equivalent to void... which is illegal? template ::value>::type...> void test(T) {} I tried this…
Hui
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x := [...]string{"Sat", "Sun"} vs x:= []string{"Sat", "Sun"}

In the go lang spec they used three dots in one of the examples: days := [...]string{"Sat", "Sun"} // len(days) == 2 Does it make any difference if the three dots are left out?
Rusty Rob
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C++11 variadic templates: return tuple from variable list of vectors

I want to write something similar to python zip (http://docs.python.org/2/library/functions.html). zip should take in a variable number of vectors of different types and it returns a vector of tuples, truncated to the length of the shortest…
duli
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Code I've never seen in C++11

I'm looking at this source code template struct conv2bin; template struct conv2bin { static_assert(high == '0' || high == '1', "no bin num!"); static int const value = (high - '0')…
Paul
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Can X x(t...) ever result in a function declaration with vexing parse?

I was writing a function template as template void f(T ...t) { X x(t...); // ... } When I was looking at it, I was wondering what happens for a call f(). Will vexing parse make x a function declaration? Compilers seem to make it…
Johannes Schaub - litb
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How to pass a reference through a parameter pack?

I have the following code: #include template void foo(Fun f, Args... args) { f(args...); } int main() { int a = 2; int b = 1000; foo([](int &b, int a){ b = a; }, b, a); std::printf("%d\n",…
p12
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Template template parameters and variadic templates with gcc 4.4

I'm using gcc 4.4 on Debian squeeze. Consider the following code. #include #include using std::map; using std::string; // Args lets the user specify additional explicit template arguments template
Faheem Mitha
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How to make grouped or paired fold of parameter pack?

template std::wstring descf(Msg, Args&&... args) { std::wostringstream woss; owss << Msg << ". " << ... << " " << args << ": '" << args << "' ";//not legal at all //or owss << Msg << ". " << args[0] << ":…
darune
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Transform variadic template parameters to another types

How to transform types from variadic template parameters to another type? For example: template struct single { std::tuple m_single; }; template struct sequences { single get(size_t pos) { …
Max
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