A library for C++20 that introduced std::ranges namespace, which consists of rangified algorithms from
Questions tagged [std-ranges]
379 questions
5
votes
1 answer
Get rid of nested for loops with std::ranges
Let I have a code:
for (auto& a : x.as)
{
for (auto& b : a.bs)
{
for (auto& c : b.cs)
{
for (auto& d : c.ds)
{
if (d.e == ..)
{
return ...
…
w00drow
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5
votes
1 answer
C++20 std::ranges: Range adapter to skip every nth element
I'm trying to get more acquainted with C++20's std::ranges implementation, and I've come across a seemingly simple problem of which I cannot find a standard solution without rolling my own implementation.
The problem is simple: I would like to only…
Human-Compiler
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5
votes
1 answer
What is the purpose of (void) casts in the GCC standard library implementation?
In the implementation of std::ranges::transform in GCC's stdlibc++, why does the for loop iterator increment have a (void) cast?
for (; __first1 != __last1 && __first2 != __last2;
++__first1, (void)++__first2, ++__result)
uselessgoddess
- 133
- 5
5
votes
0 answers
Under what circumstances does the iterator of ranges::split_view not satisfy copyable?
C++20 introduces a ranges::split_view, which accepts a view and a delimiter, and splits the view into subranges according to the delimiter.
The delimiter is also a view, and when it is a single element, it will be wrapped in a…
康桓瑋
- 33,481
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5
votes
1 answer
Why does views::reverse not work with iota_view
I have the following C++ program, and for some reason I can not use int64_t as template argument.
#include
#include
template
void fn() {
for (auto val : std::ranges::iota_view{T{1701}, T{8473}}
…
NoSenseEtAl
- 28,205
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5
votes
1 answer
std::lexicographical_compare_three_way for ranges
Why is there std::lexicographical_compare_three_way, but no std::ranges::lexicographical_compare_three_way?
There is argument Comp in std::ranges::lexicographical_compare, but it is rather useless, because function returns bool, when one of the…
SherAndrei
- 528
- 3
- 14
5
votes
1 answer
Range-v3 view composition and views calculation parallelization
Taken from range-v3 docs, the following example demonstrates a simple composition of views pipelined to produce a range:
std::vector const vi{1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
using namespace ranges;
auto rng = vi | views::remove_if([](int…
gonidelis
- 885
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- 32
5
votes
1 answer
C++20: How to split range by size?
I want to split range {1, 2, 3, 4, 5} to range of subranges of (e.g with size of 2: {{1, 2}, {3, 4}, {5}}).
Yet std::views::split only splits by delimiter.
Is there no standard "reverse join" or something to do this?
gavrilikhin.d
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5
votes
1 answer
why can't I call `ranges::begin` on a `const filter_view`?
I can't call ranges::begin on a const filter_view
https://en.cppreference.com/w/cpp/ranges/filter_view
the begin and end doesn't seem to be const. why is that?
int main(){
std::vector v{1,2,3};
// removing const will make it compile
…
Hui
- 571
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5
votes
2 answers
C++20 Streams aka Ranges
When I use the Stream Library (http://jscheiny.github.io/Streams/api.html#) I can do similar things like in Java-Streams:
#include "Streams/source/Stream.h"
#include
using namespace std;
using namespace stream;
using namespace…
Matthias
- 135
- 10
5
votes
1 answer
What are the rules for creating your own (pipeable) ranges ::views and ::actions?
In this answer, we can see that we can create our own views. I have tried that:
template
struct squared_view : std::ranges::view_interface> {
struct iterator;
constexpr squared_view() = default;
…
Fureeish
- 12,533
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- 62
4
votes
1 answer
Why can't `ranges::begin` be called on a `const any_view`?
I have this code that fails (Explorer):
#include
#include
int main() {
std::vector a{1};
const ranges::any_view av(a);
ranges::begin(av);
}
And was in the…
Johannes Schaub - litb
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4
votes
1 answer
Does std::ranges::views::enumerate use the wrong type for indexing on GCC?
First, using Range-v3, I noticed that
std::vector v;
auto w = v | ranges::views::enumerate;
auto [x, y] = *w.begin();
static_assert(std::is_same_v);
which makes sense to me because std::size_t is the right type to use…
Enlico
- 23,259
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4
votes
1 answer
Is there a way to test that a std::ranges::views iterator is the end iterator just with the iterator?
In the following function
namespace r = std::ranges;
namespace rv = std::ranges::views;
std::optional find_first_adjacent_duplicate(std::span vals) {
auto pairs = vals | rv::slide(2);
auto adj_dup = r::find_if(pairs, [](auto&& r)…
jwezorek
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4
votes
4 answers
using ranges to filter side by side vectors while remaining readable
So imagine i have 2 vectors (for reasons to do with the framework i am working in):
std::vector valid = {false, true, true, false};
std::vector percentages = {2, 50, 3, 100};
These vectors represent a batteries validity and the…
Fantastic Mr Fox
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