Difference between revisions of "cpp/numeric/math/nan"
(std::nan(nullptr) is not defined by the standard and in fact produces a crash on linux gcc 6.3.0) |
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Converts the implementation-defined character string {{tt|arg}} into the corresponding quiet NaN value, as if by calling {{lc|std::strtod}}, {{lc|std::strtof}}, or {{lc|std::strtold}}, respectively, as follows: | Converts the implementation-defined character string {{tt|arg}} into the corresponding quiet NaN value, as if by calling {{lc|std::strtod}}, {{lc|std::strtof}}, or {{lc|std::strtold}}, respectively, as follows: | ||
| − | The call {{c|std::nan(" | + | The call {{c|std::nan("n-char-sequence")}}, where {{c|n-char-sequence}} is a sequence of digits, Latin letters, and underscores, is equivalent to the call {{c|std::strtod("NAN(n-char-sequence)", (char**)nullptr);}}. |
The call {{c|std::nan("")}} is equivalent to the call {{c|std::strtod("NAN()", (char**)nullptr);}}. | The call {{c|std::nan("")}} is equivalent to the call {{c|std::strtod("NAN()", (char**)nullptr);}}. | ||
| + | |||
| + | The call {{c|std::nan("string")}}, where {{c|string}} is neither an n-char-sequence nor an empty string, is equivalent to the call {{c|std::strtod("NAN", (char**)nullptr);}}. | ||
===Parameters=== | ===Parameters=== | ||
Revision as of 03:25, 19 May 2017
| Defined in header <cmath>
|
||
| float nanf( const char* arg ); |
(since C++11) | |
| double nan( const char* arg ); |
(since C++11) | |
| long double nanl( const char* arg ); |
(since C++11) | |
Converts the implementation-defined character string arg into the corresponding quiet NaN value, as if by calling std::strtod, std::strtof, or std::strtold, respectively, as follows:
The call std::nan("n-char-sequence"), where n-char-sequence is a sequence of digits, Latin letters, and underscores, is equivalent to the call std::strtod("NAN(n-char-sequence)", (char**)nullptr);.
The call std::nan("") is equivalent to the call std::strtod("NAN()", (char**)nullptr);.
The call std::nan("string"), where string is neither an n-char-sequence nor an empty string, is equivalent to the call std::strtod("NAN", (char**)nullptr);.
Contents |
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.
Example
#include <iostream> #include <cmath> #include <cstdint> #include <cstring> 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
| (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>)
|
| [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>)
|
| [static] |
returns a quiet NaN value of the given floating-point type (public static member function of std::numeric_limits<T>)
|
| [static] |
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
| |
