What it is
Range-v3 is a C++ library that extends the standard library with a powerful range-based API. It provides composable, lazy-evaluated views and actions on sequences, enabling expressive and functional-style operations on containers and iterators.
Range-v3 allows you to create pipelines of range-based operations such as filtering, transforming, and combining sequences. It supports lazy evaluation, composability, and integrates seamlessly with STL containers.
Installation
sudo apt install range-v3-devGetting started
The smallest useful thing you can do with it, and what each part means.
#include <range/v3/all.hpp>
#include <vector>
#include <iostream>
int main() {
std::vector<int> numbers{1,2,3,4,5,6};
for(int i : numbers | ranges::views::filter([](int n){ return n % 2 == 0; }))
std::cout << i << ' ';
return 0;
}#include <range/v3/all.hpp>
#include <vector>
#include <iostream>
int main() {
std::vector<int> numbers{1,2,3,4};
for(int i : numbers | ranges::views::transform([](int n){ return n * n; }))
std::cout << i << ' ';
return 0;
}Advanced usage
Where the library earns its place over a simpler alternative.
#include <range/v3/all.hpp>
#include <vector>
#include <iostream>
int main() {
std::vector<int> numbers{1,2,3,4,5,6,7,8,9,10};
auto result = numbers
| ranges::views::filter([](int n){ return n % 2 == 0; })
| ranges::views::transform([](int n){ return n * 10; });
for(int i : result) std::cout << i << ' ';
return 0;
}#include <range/v3/all.hpp>
#include <vector>
#include <iostream>
int main() {
std::vector<int> numbers{0,1,2,3,4,5,6,7,8,9};
auto result = numbers
| ranges::views::drop(3)
| ranges::views::take(4);
for(int i : result) std::cout << i << ' ';
return 0;
}#include <range/v3/all.hpp>
#include <vector>
#include <iostream>
int main() {
std::vector<int> a{1,2,3}, b{4,5,6};
auto combined = ranges::views::concat(a, b);
for(int i : combined) std::cout << i << ' ';
return 0;
}#include <range/v3/all.hpp>
#include <vector>
#include <iostream>
int main() {
std::vector<int> numbers{1,2,3,4,5};
numbers |= ranges::actions::reverse;
for(int i : numbers) std::cout << i << ' ';
return 0;
}Errors and fixes
The failures you are most likely to hit, and what actually resolves them.
- Compilation errors with iterators
- Ensure your container supports the required iterator category for the view or algorithm used.
- Concept check failed
- Check that types satisfy the range concepts required by the operations (e.g., input_range, forward_range).
Best practices
- Prefer lazy views over creating new containers for performance.
- Chain views for readable and expressive pipelines.
- Use actions when modifying containers in-place.
- Combine with STL algorithms where applicable.
- Include only the headers you need to reduce compile times.
Background
Why it exists, and what it was reacting to.
Range-v3 was created by Eric Niebler to explore and implement ideas for ranges in C++, many of which were later adopted into C++20. It provides a rich set of algorithms, views, and actions that make working with sequences cleaner and more intuitive compared to traditional iterator-based loops.