A library for C++20 that introduced std::ranges namespace, which consists of rangified algorithms from
Questions tagged [std-ranges]
379 questions
0
votes
1 answer
Does std::reverse_iterator work with adapted ranges?
I remember having read that the motivation for [forward.iterators]/6 (requiring that, given two iterators a and b, a == b if and only if *a and *b are bound to the same object) was to support reverse_iterators. Am I remembering…
metalfox
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1 answer
C++20 ranges - how to modify a range?
I have a vector defined as:
auto xs = std::vector(5) = { 1.0, 2.0, 3.0, 4.0, 5.0 };
and I've created a view on this vector:
auto vi = xs | std::ranges::views::drop(1);
for example. However, I'd like to convert the view data into an…
Andrew
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0
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1 answer
How to define a type for a ranges::view without defining it initially?
I need to specify different ranges::view's depending upon a variable. Such as:
#include
#include
auto main() -> int
{
std::vector xs = { 1.0, 2.0, 3.0, 4.0, 5.0 };
auto x = int(0);
auto vi;
if(x == 0)
…
Andrew
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- 16
0
votes
1 answer
Make iterator work with std::ranges functions
I have the following code for a 2D-grid iterator.
#include
using std::ranges::count_if;
using std::ranges::for_each;
#include
using std::endl;
using std::cout;
#include
using std::iterator;
using…
Richard Neumann
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0 answers
Why does the Microsoft implementation of concept std::output_iterator contain a cast of type T?
Ranges are complete in VS2019, see https://devblogs.microsoft.com/cppblog/c20-ranges-are-complete-in-visual-studio-2019-version-16-10/
Why does the output_iterator concept have a static cast in the definition below taken from the Microsoft…
René Hiemstra
- 117
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0
votes
1 answer
C++20 ranges reverse view problem in VS2019 (latest)
I'm trying to read a vector in the reverse order using a ranges::subrange view but I'm confused about how it should work. I'm aware of ranges::reverse but I'm trying to avoid using this method as a personal preference and learning experience.
My…
Andrew
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- 16
0
votes
0 answers
Filter vector with std::ranges
I'd like to get from a vector of collected Data (each has a time stamp) only the elements which are newer than a specified time. savedPublishedData is a map where i look for the id. savedPublishedData.second is thn a vector of Data (Custom Class),…
Mitch
- 27
- 5
0
votes
1 answer
std::regular_invocable and by value arguments
Is it intended that following example exhibit precondition violation?
#include
#include
#include
#include
int main() {
std::vector x{1, 2, 3, 4};
auto r = x | std::views::transform([](int…
Serikov
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1 answer
How to print a range?
I'm trying to compare 2 arrays using ranges and want to print this.
#include
#include
#include
#include
#include
int main()
{
std::array test{0, 2, 3, 8, 0, 5, 4, 0, 1};
std::array
kramer
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0
votes
1 answer
Unable to Satisfy Constraint for ranges::count()
I'm exploring the ranges functions.
struct User
{
std::string name;
int age;
std::string gender;
template friend
Os& operator<<(Os& os, User const& u)
{
return os << "\n" << std::right << std::setw(10)
…
SimpleCoder
- 45
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0
votes
2 answers
c++20 Sorting Vector of structs with structs member variable and std::ranges
I have a simple struct
struct MyStruct
{
int x;
}
I have a vector of MyStructs.
vector myStructs;
int n = 10;
for(auto i = 0; i < n; i++)
myStructs.push_back(MyStruct{.x = n - i});
How will I sort myStructs according to member…
Inyoung Kim 김인영
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0
votes
2 answers
Is there any possible way to get origin value using transformed iterator?
C++20 introduces the views::elements, views::keys and views::values to easily deal with range of tuple-like values:
std::vector v{std::tuple{'A', 1}, {'B', 2}, {'C', 3}};
auto it = std::ranges::find(v | std::views::elements<0>, 'B');
assert(*it ==…
康桓瑋
- 33,481
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0
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0 answers
Cannot assign ranges transform to vector after updating to VS2019 16.6
I was on an earlier version of VS2019 (16.2 I believe) and upgraded to 16.6 yesterday and suddenly working code is throwing compiler errors and I can't figure out how to clear them up.
I have the following code:
std::vector run( const…
Mordred
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0
votes
1 answer
Why doesn't libstdc++ have span::span(Container&)?
According to cppreference, in C++20, std::span is supposed to be constructible using container references:
template
constexpr span(Container& cont);
template
constexpr span(const Container& cont);
but in the…
einpoklum
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- 684
-1
votes
1 answer
Concept and ranges
I'd like to define a concepts that is true if
t.ok(c) compiles and returns a bool, where t is a template parameter of type T and c is a "concrete" type of type C
t.around(c) compiles and returns something that can be iterated over (the type of each…
R. Absil
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