A library for C++20 that introduced std::ranges namespace, which consists of rangified algorithms from
Questions tagged [std-ranges]
379 questions
10
votes
0 answers
clang++-12 couldn't find library ranges
I am testing ranges from C++ 20 , and this is my main.cpp:
#include
#include
int main()
{
auto const ints = {0,1,2,3,4,5};
auto even = [](int i) { return 0 == i % 2; };
auto square = [](int i) { return i * i; };
…
Rahn
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10
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1 answer
Vector initialisation using ranges vs lambda inline initialisation
I would like to initialise a vector by transforming the other one. I made a test with two ways of inline initialisation a transformed std::vector.
One using lambda inline initialisation (with std::transform):
std::vector foo(100,42);
…
Patryk
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- 8
9
votes
3 answers
O(1) find/contains in std::ranges::views::iota
I understand that iota can be complex(e.g. infinite), so this can not be done easily in general case, but in some cases it should be possible to do find/contains operation in O(1).
For example
int main() {
auto vals = views::iota(10'000'000'000,…
NoSenseEtAl
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Is there a way in Range-v3 to prepend or append an element to a range/view?
Range-v3 has ranges::views::drop and ranges::views::drop_last to remove elements from the front or the back of a view.
Does it offer a similar functions to prepend/append elements to a view?
For now, the shortest way I've found is to concat the…
Enlico
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9
votes
1 answer
How can I collect an istream_view into a container?
I was trying to implement a generic reduction operation for my extensions for c++20's ranges that would collect the elements of any range into a given container. To achieve that, I first created a dummy type for extracting a template template…
Fureeish
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8
votes
2 answers
If we have ranges::zip and views::transform, why do we need ranges::zip_transform?
In C++23, the ranges (sub)library has gained std::ranges::zip, which zips multiple ranges into a single range of std::tuple's (or pairs). This is nice, and precludes requiring implementing this ourselves, using boost::zip_iterator or resorting to…
einpoklum
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8
votes
1 answer
Passing std::ranges::views as parameters in C++20
I have a method that prints a list of integers (my actual method is a bit more complicated but it is also read-only):
void printElements(const std::vector &integersList)
{
std::for_each(integersList.begin(), integersList.end(), [](const…
mathripper
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8
votes
1 answer
How to use std::views::transform on a vector?
I'm trying to create a view into a vector that transforms the type. From the doc I'd read that the following should work, but the compiler output is very confusing. What am I missing?
#include
#include
int main() {
…
OutOfBound
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8
votes
1 answer
How would you implement a lazy "range factory" for C++20 ranges that just calls a generator function?
I like the idea of the lazy ranges you can make with std::views::iota but was surprised to see that iota is currently the only thing like it in the standard; it is the only "range factory" besides views::single and views::empty. There is not…
jwezorek
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8
votes
2 answers
Why does std::views::take_while from the Ranges library require a const predicate?
TL;DR: I'm playing around with ranges and the corresponding range adaptors from the Ranges library. Both range adaptors std::views::take_while and std::views::filter take a predicate to exclude certain elements from the input sequence. Why does…
honk
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8
votes
1 answer
Why does the C++20 range library have its own namespace?
Why is std::range::sort (and other range-based algorithms) implemented in the range namespace? Why isn't it defined as an overload of std::sort taking a range?
Touloudou
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Why does views::split ignore an empty sub-range after a delimiter if it's the last element of the input range?
For the following code:
#include
#include
#include
int main()
{
std::string s = " text ";
auto sv = std::ranges::views::split(s, ' ');
std::cout << std::ranges::distance(sv.begin(),…
cigien
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8
votes
2 answers
recursive application of C++20 range adaptor causes a compile time infinite loop
The ranges library in C++20 supports the expression
auto view = r | std::views::drop(n);
to remove the first n elements of a range r with the range adaptor drop.
However if I recursively drop elements from a range, the compiler enters an infinite…
ProgrammierPatrick
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7
votes
1 answer
Is it valid to use aliased containers in `ranges::to`?
Currently only MSVC supports the nifty helper ranges::to, so I am unable to validate this in another compiler. Basically I have a type alias for a STL container and as soon as I attempt to pass it to ranges::to, compilation fails. So is this a valid…
Carsten
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7
votes
3 answers
Sorting two arrays using C++23 zip view
There is a rather typical task of sorting two arrays simultaneously, assuming that same indexed elements of the arrays form virtual pairs, which are sorted. Such questions appear at least 10 years ago: boost zip_iterator and std::sort
Now this task…
Fedor
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