std::ranges::fill_n

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Example

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print_seq: (v) = {
    for v do (elem) {
        std::cout << " (elem)$";
    }
    std::cout << '\n';
}

main: () = {
    n:== 8;

    v: std::vector<std::string> = (n, "▓▓░░");
    print_seq(v);

    std::ranges::fill_n(v.begin(), n, "░░▓▓");
    print_seq(v);

    nums: std::vector = (
        :std::complex<double>=(1, 3),
        :std::complex<double>=(2, 2),
        :std::complex<double>=(4, 8));
    print_seq(nums);
    std::ranges::fill_n(nums.begin(), 2, std::complex<double>(4, 2));
    print_seq(nums);
}

Output

 ▓▓░░ ▓▓░░ ▓▓░░ ▓▓░░ ▓▓░░ ▓▓░░ ▓▓░░ ▓▓░░
 ░░▓▓ ░░▓▓ ░░▓▓ ░░▓▓ ░░▓▓ ░░▓▓ ░░▓▓ ░░▓▓
 (1,3) (2,2) (4,8)
 (4,2) (4,2) (4,8)