Questions tagged [index-sequence]
17 questions
5
votes
2 answers
Non-type template parameter for polymorphic lambda?
Is it possible to write something like this?
[](std::index_sequence s) {
};
Or this?
[](std::index_sequence s) {
}
How is the syntax for this in C++14 or C++17? Or is it not possible at all? Basically,…
Johannes Schaub - litb
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4
votes
1 answer
Pack expansion for std::array initialization using std::index_sequence
I need to initialize an std:array with N objects taking the same constructor arguments, as in std::vector(size_t, {args...}). From my search here I came up with this, which works:
template
kamedin
- 43
- 3
4
votes
1 answer
How to avoid using the "indices trick" repeatedly?
I have a class named memory_region, which is sort of like an untyped gsl::span (i.e. it's essentially a void* and a size_t), which I also use for type erasure. It thus has an as_span() method.
With this class, I have a…
einpoklum
- 118,144
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4
votes
1 answer
Using default arguments for std::index_sequence
I have difficulties to understand the following. Why does this code compile
template
auto foo2(std::index_sequence = std::make_index_sequence())
{
constexpr size_t values[] = {N_i...};
…
abraham_hilbert
- 2,221
- 1
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3
votes
3 answers
Expand std::vector into parameter pack
I have methods with the following signature:
void DoStuff(int i);
void DoStuff(int i, k);
void DoStuff(int i, int k, int l);
I have a method from where I would like to call the DoStuff methods as follows:
void CallDoStuff(const std::vector&…
Bob
- 35
- 5
3
votes
3 answers
Distribute non-type parameter pack across different template parameter packs
Is there any syntax through which I can distribute a non-type parameter pack across the parameters of a parameter pack of templates, expecting non-type packs (of different sizes)? Since this is pretty confusing I believe that an example may help to…
lightxbulb
- 1,251
- 12
- 29
3
votes
2 answers
Creating a structure with an expanded index sequence
I want to be able to use parameter pack expansion in the initializer list of constructors. Is the best way to achieve this, to endow my class with a parameter pack template argument? Here is an example of what I…
lightxbulb
- 1,251
- 12
- 29
3
votes
2 answers
How to iterate over std::index_sequence
I have this code in my source:
template
class DimensionPack {
public:
using Dimensions = std::index_sequence;
static const std::size_t total_dimensions = sizeof...(Dims);
std::vector…
Francis Cugler
- 7,788
- 2
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- 59
2
votes
2 answers
How to expand multiple index_sequence parameter packs to initialize 2d array in C++?
I'm trying to initialize my Matrix class with std::initializer_lists. I know I can do it with std::index_sequence, but I don't know how to expand them in one statement.
This is how I do it:
template
class Matrix {
public:
…
sshd
- 49
- 1
- 4
1
vote
1 answer
Automatically generating switch statements at compile time for sparse array indexing
Is there a way to generate compile-time switch statements, for matching indices? For example if I have a sequence 1,5,8 and I want to match it to 0,1,2, is there a way the compiler can generate a function at compile time, which when given 1,5,8…
lightxbulb
- 1,251
- 12
- 29
0
votes
2 answers
Can I calculate Speedup for OpenCL kernels with templates and std::index_sequence?
tldr; How do I implement a for loop that runs a timed function with std::index_sequence?
Okay, I'll admit that title is a little cryptic but I was looking at this question: is that possible to have a for loop in compile time with runtime or even…
Jack Benson
- 107
- 1
- 8
0
votes
1 answer
C++ Build error: expected type-specifier before [Variadic templates] class
Here is my code:
#include
#include
#include
template
inline void DispatchToMethodImpl(const Obj& obj, Method method, Args&& args,
…
Wu Jo
- 1
0
votes
1 answer
How does std::index_sequence_for() exactly work?
I have the following code
#include
#include
#include
using namespace std::literals::string_literals;
template< typename tupleType, size_t ... inds >
void printTupleH(const tupleType& tuple, std::index_sequence
asmmo
- 6,922
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0
votes
1 answer
Recursive aggregate type configured using many template parameters using std::index_sequence
There is a class template:
template
class Feature { /* Implementation goes here */ };
All the instantiations of Feature<...> are 'collected' here:
template
Martin Kopecký
- 912
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0
votes
3 answers
How Do I Unroll a Variadic Template in a Condition?
I'm looking to unroll a variadic template into separate functions used in the conjunction of an if-statement. Here's an example of what I'm trying to do:
template
bool bar(const T& param) { return param[I] != 13; }
template…
Jonathan Mee
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