NAME

std::ranges::min_element - std::ranges::min_element

Synopsis

Defined in header <algorithm>
Call signature
template< std::forward_iterator I, std::sentinel_for<I> S, class Proj =
std::identity,

std::indirect_strict_weak_order<std::projected<I, Proj>> Comp = (1) (since
ranges::less > C++20)

constexpr I min_element( I first, S last, Comp comp = {}, Proj proj = {}
);
template< ranges::forward_range R, class Proj = std::identity,

std::indirect_strict_weak_order< (since
std::projected<ranges::iterator_t<R>, Proj>> Comp = ranges::less > (2) C++20)
constexpr ranges::borrowed_iterator_t<R>

min_element( R&& r, Comp comp = {}, Proj proj = {} );

1) Finds the smallest element in the range [first, last).
2) Same as (1), but uses r as the source range, as if using ranges::begin(r) as
first and ranges::end(r) as last.

The function-like entities described on this page are niebloids, that is:

* Explicit template argument lists may not be specified when calling any of them.
* None of them is visible to argument-dependent lookup.
* When one of them is found by normal unqualified lookup for the name to the left
of the function-call operator, it inhibits argument-dependent lookup.

In practice, they may be implemented as function objects, or with special compiler
extensions.

Parameters

first, last - iterator-sentinel pair denoting the range to examine
r - the range to examine
comp - comparison to apply to the projected elements
proj - projection to apply to the elements

Return value

Iterator to the smallest element in the range [first, last). If several elements in
the range are equivalent to the smallest element, returns the iterator to the first
such element. Returns first if the range is empty.

Complexity

Exactly max(N-1,0) comparisons, where N = ranges::distance(first, last).

Possible implementation

struct min_element_fn {
template<std::forward_iterator I, std::sentinel_for<I> S, class Proj = std::identity,
std::indirect_strict_weak_order<std::projected<I, Proj>> Comp = ranges::less>
constexpr I operator()(I first, S last, Comp comp = {}, Proj proj = {}) const
{
if (first == last) {
return last;
}

auto smallest = first;
++first;
for (; first != last; ++first) {
if (!std::invoke(comp, std::invoke(proj, *smallest), std::invoke(proj, *first))) {
smallest = first;
}
}
return smallest;
}

template<ranges::forward_range R, class Proj = std::identity,
std::indirect_strict_weak_order<
std::projected<ranges::iterator_t<R>, Proj>> Comp = ranges::less>
constexpr ranges::borrowed_iterator_t<R>
operator()(R&& r, Comp comp = {}, Proj proj = {}) const
{
return (*this)(ranges::begin(r), ranges::end(r), std::ref(comp), std::ref(proj));
} };

inline constexpr min_element_fn min_element;

Example

// Run this code

#include <algorithm>
#include <iostream>
#include <vector>
#include <cmath>

int main()
{
std::vector<int> v{ 3, 1, -14, 1, 5, 9 };

namespace ranges = std::ranges;
auto result = ranges::min_element(v.begin(), v.end());
std::cout << "min element at: " << ranges::distance(v.begin(), result) << '\n';

auto abs_compare = [](int a, int b) { return (std::abs(a) < std::abs(b)); };
result = ranges::min_element(v, abs_compare);
std::cout << "min element (absolute) at: " << ranges::distance(v.begin(), result) << '\n';
}

Output:

min element at: 2
min element (absolute) at: 1