std::nan, std::nanf, std::nanl
From cppreference.com
Defined in header <cmath>
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float nanf(
const
char
* arg )
;
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(1) | (since C++11) |
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double nan (
const
char
* arg )
;
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(2) | (since C++11) |
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long
double nanl(
const
char
* arg )
;
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(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
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)
;
Parameters
| arg | - | narrow character string identifying the contents of a NaN |
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.
Error handling
This function is not subject to any of the error conditions specified in math_errhandling.
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)See also
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(C++11)
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checks if the given number is NaN (function) |
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(C++11)
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evaluates to a quiet NaN of type float (macro constant) |
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[static]
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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]
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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]
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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]
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returns a signaling NaN value of the given floating-point type (public static member function of std::numeric_limits<T>) |
C documentation for nanf, nan, nanl
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