std::setbase(3)

💅 std::setbase 💅

okay so this is the C++ Standard Libary manual, page std::setbase(3) — group-chat bestie edition, no cap. (Yes, the header really spells it “Libary,” and we’re not fixing it, we’re slaying with it 💖)

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🌸 NAME 🌸

• std::setbase - std::setbase — that’s the whole name, bestie, it’s giving minimalist icon behavior 💅

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📜 Synopsis 📜

Defined in header <iomanip> ✨

/*unspecified*/ setbase( int base );

Sets the numeric base of the stream. When used in an expression out << setbase(base) or in in >> setbase(base), changes the basefield flag of the stream out or in, depending on the value of base:

• the value 16 sets basefield to std::ios_base::hex.
• the value 8 sets std::ios_base::oct.
• the value 10 sets std::ios_base::dec.

Values of base other than 8, 10, or 16 reset basefield to zero, which corresponds to decimal output and prefix-dependent input. periodt. 💅

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🎛️ Parameters 🎛️

• base — new value for basefield

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🎁 Return value 🎁

An object of unspecified type such that

• if out is an object of type std::basic_ostream<CharT, Traits>, the expression out << setbase(base)
  • has type std::basic_ostream<CharT, Traits>&
  • has value out
  • behaves as if it called f(out, base)
• if in is an object of type std::basic_istream<CharT, Traits>, the expression in >> setbase(base)
  • has type std::basic_istream<CharT, Traits>&
  • has value in
  • behaves as if it called f(in, base)

where the function f is defined as:

void f(std::ios_base& str, int base)
{
    // set basefield
    str.setf(base == 8 ? std::ios_base::oct :
        base == 10 ? std::ios_base::dec :
        base == 16 ? std::ios_base::hex :
        std::ios_base::fmtflags(0), std::ios_base::basefield);
}

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💻 Example 💻

okay, // Run this code energy — here’s the whole thing, bestie 👇

#include <iomanip>
#include <iostream>
#include <sstream>

int main()
{
    std::cout << "Parsing string \"10 0x10 010\"\n";

    int n1, n2, n3;
    std::istringstream s("10 0x10 010");

    s >> std::setbase(16) >> n1 >> n2 >> n3;
    std::cout << "hexadecimal parse: " << n1 << ' ' << n2 << ' ' << n3 << '\n';

    s.clear();
    s.seekg(0);

    s >> std::setbase(0) >> n1 >> n2 >> n3;
    std::cout << "prefix-dependent parse: " << n1 << ' ' << n2 << ' ' << n3 << '\n';

    std::cout << "hex output: " << std::setbase(16)
              << std::showbase << n1 << ' ' << n2 << ' ' << n3 << '\n';
}

📤 Output 📤

Parsing string "10 0x10 010"
hexadecimal parse: 16 16 16
prefix-dependent parse: 10 16 8
hex output: 0xa 0x10 0x8

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🩹 Defect reports 🩹

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

• LWG 183, applied to C++98 — behavior as published: setbase could only be used with streams of type std::ostream or std::istream; correct behavior: usable with any character stream. glow-up confirmed ✨

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👀 See also 👀

• dec — changes the base used for integer I/O
• hex — (function)
• oct
• showbase — controls whether prefix is used to indicate numeric base
• noshowbase — (function)

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that’s the whole page, bestie 🫶 this little gem is from http://cppreference.com, dated 2024.06.10, and the manual footer says std::setbase(3). mwah 💋