std::numeri...::quiet_NaN(3)

🌸 NAME 🌸

Okay bestie, welcome to the page for std::numeric_limits::quiet_NaN — the manual header calls it std::numeri...::quiet_NaN(3) and says it's from the C++ Standard Libary (their spelling, not mine 💅). The NAME line is literally std::numeric_limits::quiet_NaN - std::numeric_limits::quiet_NaN, which is giving “I contain multitudes but also just my own name.” 🫶

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🦋 Synopsis 🦋

static T quiet_NaN() throw();             (until C++11)
static constexpr T quiet_NaN() noexcept;  (since C++11)

Returns the special value "quiet not-a-number", as represented by the floating-point type T. Only meaningful if std::numeric_limits<T>::has_quiet_NaN == true. In IEEE 754, the most common binary representation of floating-point numbers, any value with all bits of the exponent set and at least one bit of the fraction set represents a NaN. It is implementation-defined which values of the fraction represent quiet or signaling NaNs, and whether the sign bit is meaningful.

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💖 Return value 💖

Here's the whole return-value roster, no gatekeeping, no skipped entries:

• T — std::numeric_limits<T>::quiet_NaN()
• /* non-specialized */ — T()
• bool — false
• char — 0
• signed char — 0
• unsigned char — 0
• wchar_t — 0
• char8_t (since C++20) — 0
• char16_t (since C++11) — 0
• char32_t (since C++11) — 0
• short — 0
• unsigned short — 0
• int — 0
• unsigned int — 0
• long — 0
• unsigned long — 0
• long long (since C++11) — 0
• unsigned long long (since C++11) — 0
• float — implementation-defined (may be NAN)
• double — implementation-defined
• long double — implementation-defined

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🎀 Notes 🎀

Two little caveats with main-character energy:

• A NaN never compares equal to itself.
• Copying a NaN may not preserve its bit representation.

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🌈 Example 🌈

Several ways to generate a NaN (the output string is compiler-specific). The page also has a literal // Run this code line right before the snippet, so here's the snippet:

#include <iostream>
#include <limits>
#include <cmath>

int main()
{
    std::cout << std::numeric_limits<double>::quiet_NaN()     << ' ' // nan
              << std::numeric_limits<double>::signaling_NaN() << ' ' // nan
              << std::acos(2)    << ' '   // nan
              << std::tgamma(-1) << ' '   // nan
              << std::log(-1)    << ' '   // nan
              << std::sqrt(-1)   << ' '   // -nan
              << 0 / 0.0         << '\n'; // -nan

    std::cout << "NaN == NaN? " << std::boolalpha
              << ( std::numeric_limits<double>::quiet_NaN() ==
                   std::numeric_limits<double>::quiet_NaN() ) << '\n';
}

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⭐ Possible output ⭐

nan nan nan nan nan -nan -nan
NaN == NaN? false

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👑 See also 👑

• has_quiet_NaN — identifies floating-point types that can represent the special value "quiet not-a-number" (NaN) [static] (public static member constant)
• signaling_NaN — returns a signaling NaN value of the given floating-point type [static] (public static member function)
• nan, nanf, nanl — not-a-number (NaN) (C++11) (function) (C++11) (C++11)
• isnan — checks if the given number is NaN (C++11) (function)

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Alright bestie, that's the whole page 💖 — source http://cppreference.com, date 2024.06.10, and the page is std::numeri...::quiet_NaN(3). Stay floaty! 🌈✨