std::array is a container that encapsulates constant size arrays in C++.
std::array is a part of the C++ Standard Library since C++11.
Reference: https://en.cppreference.com/w/cpp/container/array
Questions tagged [stdarray]
433 questions
148
votes
6 answers
Passing a std::array of unknown size to a function
In C++11, how would I go about writing a function (or method) that takes a std::array of known type but unknown size?
// made up example
void mulArray(std::array& arr, const int multiplier) {
for(auto& e : arr) {
e *=…
Adrian
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145
votes
7 answers
std::array vs array performance
If I want to build a very simple array like:
int myArray[3] = {1,2,3};
Should I use std::array instead?
std::array a = {{1, 2, 3}};
What are the advantages of using std::array over usual ones? Is it more performant? Just easier to handle…
Arcyno
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145
votes
5 answers
Default initialization of std::array?
With C++11 std::array, do I have the guarantee that the syntax std::array x; will default-initialize all the elements of the array ?
EDIT: if not, is there a syntax that will work on all arrays (including zero-sized arrays) to initialize all…
Vincent
- 57,703
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88
votes
5 answers
Why does std::array not have an constructor that takes a value for the array to be filled with?
Is the absence of
std::array::array(const T& value);
an oversight? It seems mighty useful to me, and dynamic containers (like std::vector) do have a similar constructor.
I am fully aware of
std::array::fill(const T& value);
but…
rubenvb
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62
votes
2 answers
How to create std::array with initialization list without providing size directly
How can I make a3 compile?
int main()
{
int a1[] = { 1, 2, 3 };
std::array a2 = { 1, 2, 3 };
std::array a3 = { 1, 2, 3 };
}
It's very inconvenient, and brittle, to hard-code the size of the array when using an…
Neil Kirk
- 21,327
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57
votes
6 answers
Get size of std::array without an instance
Given this struct:
struct Foo {
std::array bar;
};
How can I get the number of elements of the bar array if I don't have an instance of Foo?
ChronoTrigger
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49
votes
4 answers
What is the memory layout of vector of arrays?
can anybody explaine the memory layout of
std::vector> vec(2)
does it provide contiguous memory block of a 2D array
with 2 rows of 5 elements?
To my understanding, the vector of vectors
std::vector> vec(2,…
Const
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47
votes
8 answers
Initializing a std::array with a constant value
I need to initialize all elements of a std::array with a constant value, like it can be done with std::vector.
#include
#include
int main()
{
std::vector v(10, 7); // OK
std::array a(7); // does not…
Jabberwocky
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47
votes
4 answers
Is there a reason for zero sized std::array in C++11?
Consider the following piece of code, which is perfectly acceptable by a C++11 compiler:
#include
#include
auto main() -> int {
std::array A;
for(auto i : A) std::cout << i << std::endl;
return 0;
}
According…
101010
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41
votes
3 answers
Convenient way to declare 2D (or even higher dimension) arrays with std::array
I'm about to convert a lot of old C++ code to more modern C++.
There are many raw 2D arrays in that code like:
Foo bar[XSIZE][YSIZE];
And I'm about to replace these declarations with
std::array, XSIZE> bar;
This is a…
Jabberwocky
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40
votes
3 answers
Initialize an std::array algorithmically at compile time
Consider:
static constexpr unsigned num_points{ 7810 };
std::array< double, num_points > axis;
for (int i = 0; i < num_points; ++i)
{
axis[i] = 180 + 0.1 * i;
}
axis is a class-wide constant. I want to avoid initializing it like any other…
Vorac
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35
votes
2 answers
How should I brace-initialize an std::array of std::pairs?
std::array, 2> ids = { { 0, 1 }, { 1, 2 } };
VS2013 error:
error C2440: 'initializing' : cannot convert from 'int' to 'std::pair' No constructor could take the source type, or constructor overload resolution was…
Neil Kirk
- 21,327
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35
votes
1 answer
Does using std::array lead to code bloat?
I have seen in a few places the recommendation to use std::array over C-style arrays in C++, claiming it is a better, safer alternative with no overhead. See:
The standard container array [...] has no space overheads beyond what
it needs to hold…
frangio
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29
votes
1 answer
Call to implicitly-deleted default constructor
I get the error message Call to implicitly-deleted default constructor of 'std::array' when I try to compile my C++ project.
Header file cubic_patch.hpp
#include
class Point3D{
public:
Point3D(float, float, float);
private:
float…
Itsbananas
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28
votes
1 answer
Is it undefined behavior to iterate over an std::array initialized in the for-loop?
// This snippet
for (const float t : std::array{ 0.0f, 0.33f, 0.66f, 1.0f }) {
std::cout << "t = " << t << "\n";
}
// Yields the following (incorrect) values:
t = -3.91649e-28
t = 4.59037e-41
t = 2.66247e-44
t = 0
// Whereas this snippet ...
auto…
Viktor Sehr
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