Comparing Only Part of Two Ranges
Can I use std::ranges::equal() to compare only a part of two ranges?
Yes, you can use std::ranges::equal() to compare only a part of two ranges by specifying subranges.
This can be done using iterator pairs or views to define the portions of the ranges you want to compare.
Here's an example that demonstrates comparing parts of two vectors:
#include <algorithm>
#include <iostream>
#include <ranges>
#include <vector>
int main() {
std::vector<int> vec1{1, 2, 3, 4, 5};
std::vector<int> vec2{10, 2, 3, 40, 50};
auto subrange1 = std::ranges::subrange(
vec1.begin() + 1, vec1.begin() + 3);
auto subrange2 = std::ranges::subrange(
vec2.begin() + 1, vec2.begin() + 3);
if (std::ranges::equal(subrange1, subrange2)) {
std::cout << "Subranges are equal\n";
} else {
std::cout << "Subranges are not equal\n";
}
}Subranges are equalIn this example, subrange1 and subrange2 represent parts of vec1 and vec2, respectively.
Specifically, they represent the elements from the second to the fourth element (inclusive).
The std::ranges::equal() function compares these subranges and prints the result.
Alternatively, you can use views to achieve the same result:
#include <algorithm>
#include <iostream>
#include <ranges>
#include <vector>
int main() {
std::vector<int> vec1{1, 2, 3, 4, 5};
std::vector<int> vec2{10, 2, 3, 40, 50};
auto view1 = vec1
| std::views::drop(1)
| std::views::take(2);
auto view2 = vec2
| std::views::drop(1)
| std::views::take(2);
if (std::ranges::equal(view1, view2)) {
std::cout << "Views are equal\n";
} else {
std::cout << "Views are not equal\n";
}
}Views are equalIn this example, std::views::drop(1) and std::views::take(3) are used to create views of the specified subranges.
The std::ranges::equal() function then compares these views.
Using subranges or views allows you to compare only specific parts of your ranges, making std::ranges::equal() a flexible tool for various comparison needs.
8 Key Standard Library Algorithms
An introduction to 8 more useful algorithms from the standard library, and how we can use them alongside views, projections, and other techniques