Questions tagged [parameter-pack]
171 questions
4
votes
2 answers
Combining function parameter pack and default arguments
I have a function with a parameter pack:
template
void tprintf(const char* format, Targs... args) {}
(the implementation shouldn't matter, just the signature). I want to add source position as default argument, using the…
Alexey Romanov
- 167,066
- 35
- 309
- 487
4
votes
1 answer
Must I explicitly show the types in the parameter pack when instantiate a template?
I got a example to illustrate my question:
#include
class Foo {
public:
Foo(int i) {}
};
template
class Bar {
public:
T t;
Bar(Args &&... args) : t(std::forward(args)...) {}
};
and if I want…
user2269707
3
votes
1 answer
Can we use int... as an argument for template parameter pack directly?
Here is my problem:
template
struct iniClass
{
private:
std::initializer_list m_data;
int x;
public:
iniClass(Ts... vars)
: m_data({vars...}), x(8)
{
std::cout << "created object with first…
Rango
- 217
- 8
3
votes
3 answers
Remapping a tuple onto another tuple
I am attempting to convert between two types of std::tuples but I'm having trouble getting the implementation right. I want it to map if the type is the same, but it needs to allow duplicate types to get mapped in the original order.
The basic…
bpmckinnon
- 125
- 4
3
votes
2 answers
How to specify a default argument for a template parameter pack?
I have the following method
template
void doSomething()
{
...
};
It seems not possible to supply default values for Indices, e.g.
template
zhanginou
- 177
- 6
3
votes
1 answer
unpack a parameter pack of pairs into an array and a tuple
So i have a list of pairs where the first member is a constant integer and the second is a type, is there anyway to unpack it into an array of the first member and a tuple of the second members?
struct MA {}
struct MB {}
struct MC {}
template
fluter
- 13,238
- 8
- 62
- 100
3
votes
2 answers
Compile-time set subtraction of two tuples
I have an application where I am constructing tuple out of a parameter pack:
template
struct foo {
typedef std::tuple A;
}
And I have another tuple-type B defined as:
typedef std::tuple B;
Is there a way to obtain a…
Blizzard
- 1,117
- 2
- 11
- 28
3
votes
2 answers
Get member from last possible class of a parameter pack
I want to get the value of a member variable of the last possible class in a parameter pack.
For eg. I want getLastB(a_, b_, c_, d_) to return 100 in the code below (the value of c_.b), and not 40 (the value of b_.b)
#include
#include…
Priyank Palod
- 105
- 6
3
votes
1 answer
Incrementing every value in a parameter pack
I am currently attempting to increment every value in a parameter pack full of std::vector::iterators of some unknown type. I am currently struggling to get my head around how the ... syntax works. I would have thought to increment every value it…
finlay morrison
- 225
- 1
- 5
3
votes
2 answers
Template specialization with Parameter Packs
I'm quite new to c++ but wanted to try to do some fancy template stuff. I am not sure if it is possible, but I am fairly confident there is a way to achieve that.
So here's the Issue:
I am calling various Hardware function, which requires a number…
Abudinka
- 85
- 6
3
votes
0 answers
Does std::thread use parameter packs and if yes then how? :)
I want to achieve a similar result:
void somefunc(int var1, char var2){
dosomething();
}
int main(){
std::thread t1(somefunc, 'a', 3);
return EXIT_SUCCESS;
}
std::thread takes a function pointer and any number of argments. In my class that…
DominikRzecki
- 43
- 5
3
votes
1 answer
Divorce a parameter pack in a class template
I am trying to write a class template that uses a parameter-pack and implements a member function for each type contained in the parameter-pack.
This is what I have so far:
template
class Myclass {
public:
void…
flashbanger
- 53
- 2
3
votes
2 answers
How to construct different object according to their types in a template function?
Here is my question, I have a base class Base, two derived classes ClassA and ClassB form Base taking only two arguments, and two classes ClassB0 and ClassB1 derived from ClassB taking three arguments. I want to create class intance accroding to the…
matthiascy
- 75
- 5
2
votes
1 answer
Inheritance from variadic and construction with parameter pack : default constructor
I have that code :
template
class Variable : virtual public GenericVar, public Extentions...
{
static_assert((std::is_base_of_v, Extentions> && ...), "Only virtual base of…
Slane
- 21
- 2
2
votes
2 answers
method with template parameter pack is called recursivly indefenetly, and doesnt call overloaded method
I have a logging class, which logs messages of any type:
/// log level enum
enum level_t
{
DEBUG, // used for debugging output
CPLEX, // used for cplex output
INFO, // used for generell informative output
WARNING, // used for…
Moritz
- 378
- 5
- 14