std::resetiosflags(3)

💅 std::resetiosflags(3) — C++ Standard Libary 💅

std::resetiosflags — yep, the NAME is literally std::resetiosflags; that's the whole name, bestie. Iconic behavior, minimal branding.

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🦋 Synopsis 🦋

Defined in header <iomanip>:

/*unspecified*/ resetiosflags( std::ios_base::fmtflags mask );

When you use it in an expression like out << resetiosflags(mask) or in >> resetiosflags(mask), it clears all format flags of the stream out or in as specified by the mask. It's giving "clean slate" energy, fr fr.

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🍓 Parameters 🍓

• mask — bitmask of the flags to clear. That's the whole parameter. Slay.

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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 << resetiosflags(mask)

• has type std::basic_ostream<CharT, Traits>&
• has value out
• behaves as if it called f(out, mask)

• if in is an object of type std::basic_istream<CharT, Traits>, the expression

in >> resetiosflags(mask)

• has type std::basic_istream<CharT, Traits>&
• has value in
• behaves as if it called f(in, mask)

where the function f is defined as:

void f(std::ios_base& str, std::ios_base::fmtflags mask)
{
    // reset specified flags
    str.setf(ios_base::fmtflags(0), mask);
}

The return type is literally unspecified — do not try to name it, bestie. The vibe is "trust the manipulator," not "collect the type." 🙈

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🎀 Example 🎀

The page says // Run this code — so run it, bestie:

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

int main()
{
    std::istringstream in("10 010 10 010 10 010");
    int n1, n2;

    in >> std::oct >> n1 >> n2;
    std::cout << "Parsing \"10 010\" with std::oct gives: " << n1 << ' ' << n2 << '\n';

    in >> std::dec >> n1 >> n2;
    std::cout << "Parsing \"10 010\" with std::dec gives: " << n1 << ' ' << n2 << '\n';

    in >> std::resetiosflags(std::ios_base::basefield) >> n1 >> n2;
    std::cout << "Parsing \"10 010\" with autodetect gives: " << n1 << ' ' << n2 << '\n';
}

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🌈 Output 🌈

Parsing "10 010" with std::oct gives: 8 8
Parsing "10 010" with std::dec gives: 10 10
Parsing "10 010" with autodetect gives: 10 8

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🧚 Defect reports 🧚

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

• DR LWG 183, applied to C++98 — behavior as published: resetiosflags 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 👑

• setf — sets specific format flag; public member function of std::ios_base.
• setiosflags — sets the specified ios_base flags; function.

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With love from cppreference.com, version 2024.06.10, page std::resetiosflags(3) 💖