std::nan, std::nanf, std::nanl
From cppreference.com
| Defined in header <cmath>
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| float nanf( const char* arg ); |
(1) | (since C++11) |
| double nan ( const char* arg ); |
(2) | (since C++11) |
| long double nanl( const char* arg ); |
(3) | (since C++11) |
Converts the character string arg into the corresponding quiet NaN value, as if by calling std::strtof, std::strtod, or std::strtold, respectively.
1) The call std::nanf("n-char-sequence"), where n-char-sequence is a sequence of digits, ASCII letters, and underscores, is equivalent to the call std::strtof("NAN(n-char-sequence)", (char**)nullptr);.
The call std::nanf("") is equivalent to the call std::strtof("NAN()", (char**)nullptr);.
The call std::nanf("string"), where string is neither an n-char-sequence nor an empty string, is equivalent to the call std::strtof("NAN", (char**)nullptr);.
Contents |
[edit] Parameters
| arg | - | narrow character string identifying the contents of a NaN |
[edit] Return value
The quiet NaN value that corresponds to the identifying string arg or zero if the implementation does not support quiet NaNs.
If the implementation supports IEEE floating-point arithmetic (IEC 60559), it also supports quiet NaNs.
[edit] Error handling
This function is not subject to any of the error conditions specified in math_errhandling.
[edit] Example
Run this code
#include <cmath> #include <cstdint> #include <cstring> #include <iostream> int main() { double f1 = std::nan("1"); std::uint64_t f1n; std::memcpy(&f1n, &f1, sizeof f1); std::cout << "nan(\"1\") = " << f1 << " (" << std::hex << f1n << ")\n"; double f2 = std::nan("2"); std::uint64_t f2n; std::memcpy(&f2n, &f2, sizeof f2); std::cout << "nan(\"2\") = " << f2 << " (" << std::hex << f2n << ")\n"; }
Possible output:
nan("1") = nan (7ff0000000000001)
nan("2") = nan (7ff0000000000002)[edit] See also
| (C++11) |
checks if the given number is NaN (function) |
| (C++11) |
evaluates to a quiet NaN of type float (macro constant) |
| [static] |
identifies floating-point types that can represent the special value "quiet not-a-number" (NaN) (public static member constant of std::numeric_limits<T>)
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| [static] |
identifies floating-point types that can represent the special value "signaling not-a-number" (NaN) (public static member constant of std::numeric_limits<T>)
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| [static] |
returns a quiet NaN value of the given floating-point type (public static member function of std::numeric_limits<T>)
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| [static] |
returns a signaling NaN value of the given floating-point type (public static member function of std::numeric_limits<T>)
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| C documentation for nanf, nan, nanl
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