template<class T> constexpr const T&
clamp(const T& v, const T& lo, const T& hi);

template<class T, class Compare> constexpr const T&
clamp(const T& v, const T& lo, const T& hi, Compare comp);

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

static void
clamp_range(auto begin, auto end, auto out, auto lo, auto hi)
{
    for (auto it=begin; it < end; ++it) {
        *out = std::clamp(*it, lo, hi);
        ++out;
    }
}

int main()
{
    std::vector<int> v{1, 2, 3, 4, 5, 6, 7, 8, 9};
    clamp_range(std::begin(v), std::end(v), std::begin(v), 3, 7);
    for (auto it : v) {
        std::cout << it << '\n';
    }
    return 0;
}

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