std::experi...cal_compare(3)

💖 std::experimental::ranges::lexicographical_compare(3) 💖

okay so bestie, we are deep in the C++ Standard Libary manual, and this page is serving std::experimental::ranges::lexicographical_compare realness. Yes, the name is long enough to need its own snack break. 🍓

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🌸 NAME 🌸

std::experimental::ranges::lexicographical_compare — std::experimental::ranges::lexicographical_compare

(not me giving you the same name twice, it's just built like that 💅)

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✨ Synopsis ✨

Defined in header <experimental/ranges/algorithm> — write that down, bestie. 🎀

this overload is (1) (ranges TS):

template< InputIterator I1, Sentinel<I1> S1, InputIterator I2, Sentinel<I2> S2,
          class Proj1 = ranges::identity, class Proj2 = ranges::identity,
          class Comp = ranges::less<> >
    requires IndirectStrictWeakOrder<Comp, projected<I1, Proj1>, projected<I2, Proj2>>
bool lexicographical_compare( I1 first1, S1 last1, I2 first2, S2 last2,
                              Comp comp = Comp{},
                              Proj1 proj1 = Proj1{}, Proj2 proj2 = Proj2{} );

and this overload is (2) (ranges TS):

template< InputRange R1, InputRange R2,
          class Proj1 = ranges::identity, class Proj2 = ranges::identity,
          class Comp = ranges::less<> >
    requires IndirectStrictWeakOrder<Comp,
        projected<ranges::iterator_t<R1>, Proj1>,
        projected<ranges::iterator_t<R2>, Proj2>>
bool lexicographical_compare( R1&& r1, R2&& r2, Comp comp = Comp{},
                              Proj1 proj1 = Proj1{}, Proj2 proj2 = Proj2{} );

1. Checks if the first range [first1, last1) is lexicographically less than the second range [first2, last2). Elements are compared using the given binary comparison function comp, after being projected with proj1 and proj2 respectively. 🔥
2. Same as (1), but uses r1 as the first source range and r2 as the second source range, as if using ranges::begin(r1) as first1, ranges::end(r1) as last1, ranges::begin(r2) as first2, and ranges::end(r2) as last2. 🦋

Lexicographical comparison is an operation with the following properties:

• Two ranges are compared element by element.
• The first mismatching element defines which range is lexicographically less or greater than the other.
• If one range is a prefix of another, the shorter range is lexicographically less than the other.
• If two ranges have equivalent elements and are of the same length, then the ranges are lexicographically equal.
• An empty range is lexicographically less than any non-empty range.
• Two empty ranges are lexicographically equal.

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🫶 Parameters 🫶

• first1, last1 — the first range of elements to examine
• r1 — the first range of elements to examine
• first2, last2 — the second range of elements to examine
• r2 — the second range of elements to examine
• comp — comparison function to apply to the projected elements
• proj1 — projection to apply to the elements in the first range
• proj2 — projection to apply to the elements in the second range

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💜 Return value 💜

true if the first range is lexicographically less than the second.

That's it. That's the tea. 🫖

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🧚 Complexity 🧚

At most 2·min(N1, N2) applications of the comparison operation, where N1 = last1 - first1 and N2 = last2 - first2.

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👑 Possible implementation 👑

template<InputIterator I1, Sentinel<I1> S1, InputIterator I2, Sentinel<I2> S2,
         class Proj1 = ranges::identity, class Proj2 = ranges::identity,
         class Comp = ranges::less<>>
    requires IndirectStrictWeakOrder<Comp, projected<I1, Proj1>, projected<I2, Proj2>>
bool lexicographical_compare(I1 first1, S1 last1, I2 first2, S2 last2,
                             Comp comp = Comp{},
                             Proj1 proj1 = Proj1{}, Proj2 proj2 = Proj2{})
{
    for (; (first1 != last1) && (first2 != last2); (void) ++first1, (void) ++first2)
    {
        if (ranges::invoke(comp, ranges::invoke(proj1, *first1),
                                 ranges::invoke(proj2, *first2)))
            return true;
        if (ranges::invoke(comp, ranges::invoke(proj2, *first2),
                                 ranges::invoke(proj1, *first1)))
            return false;
    }
    return (first1 == last1) && (first2 != last2);
}

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🍓 Example 🍓

This section is incomplete.

Reason: no example.

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🌈 See also 🌈

• lexicographical_compare — returns true if one range is lexicographically less than another (function template)
• equal — determines if two sets of elements are the same (function template)

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💀 Category 💀

• Todo no example

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💖 source: http://cppreference.com · version/date: 2024.06.10 · footer page: std::experi...cal_compare(3) 💖