std::basic_...iew::substr(3)

💖 NAME 💖

std::basic_string_view::substr — yep, bestie, it's literally std::basic_string_view::substr. The page header calls this one std::basic_...iew::substr(3) from the C++ Standard Libary (that spelling is the page's, not mine 😭), and it's the member that hands you a substring view.

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✨ Synopsis ✨

Okay so here's the whole signature, and yes it's constexpr:

constexpr basic_string_view substr( size_type pos = 0,
                                    size_type count = npos ) const;

since C++17 — it's giving modern-standard energy, no cap.

It returns a view of the substring [pos, pos + rlen), where rlen is the smaller of count and size() - pos. Slicey. Iconic. Periodt. 🎀

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🌸 Parameters 🌸

• pos — position of the first character.
• count — requested length.

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🦋 Return value 🦋

View of the substring [pos, pos + rlen). That's the whole vibe. 💅

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😭 Exceptions 😭

std::out_of_range if pos > size().

fr fr, if pos is bigger than size(), it throws std::out_of_range — do not test that boundary unless you're ready for the drama.

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⚡ Complexity ⚡

Constant. Literally constant. Effortless. ✨

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💻 Example 💻

// Run this code

#include <cstddef>
#include <iostream>
#include <stdexcept>
#include <string_view>

int main()
{
    typedef std::size_t count_t, pos_t;

    constexpr std::string_view data{"ABCDEF"};

    std::cout << data.substr() << '\n'; // ABCDEF, i.e. data[0, 5] that is [0, 6)
    std::cout << data.substr(pos_t(1)) << '\n'; // BCDEF, i.e. [1, 6)
    std::cout << data.substr(pos_t(2), count_t(3)) << '\n'; // CDE, i.e. [2, 2 + 3)
    std::cout << data.substr(pos_t(4), count_t(42)) << '\n'; // EF, i.e. [4, 6)

    try
    {
        [[maybe_unused]]
        auto sub = data.substr(pos_t(666), count_t(1)); // throws: pos > size()
    }
    catch (std::out_of_range const& ex)
    {
        std::cout << ex.what() << '\n';
    }
}

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🔥 Possible output 🔥

ABCDEF
BCDEF
CDE
EF
basic_string_view::substr: __pos (which is 666) > __size (which is 6)

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👑 See also 👑

• copy — copies characters (public member function).
• find — find characters in the view (public member function).
• substr — returns a substring (public member function of std::basic_string<CharT,Traits,Allocator>).

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okay bye bestie 🫶 this page is from source http://cppreference.com, date/version 2024.06.10, and the manual name is std::basic_...iew::substr(3). Slay and stay safe out there 💖✨