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Reference

C library:
- <cassert> (assert.h)
- <cctype> (ctype.h)
- <cerrno> (errno.h)
- C++11
  <cfenv> (fenv.h)
- <cfloat> (float.h)
- C++11
  <cinttypes> (inttypes.h)
- <ciso646> (iso646.h)
- <climits> (limits.h)
- <clocale> (locale.h)
- <cmath> (math.h)
- <csetjmp> (setjmp.h)
- <csignal> (signal.h)
- <cstdarg> (stdarg.h)
- C++11
  <cstdbool> (stdbool.h)
- <cstddef> (stddef.h)
- C++11
  <cstdint> (stdint.h)
- <cstdio> (stdio.h)
- <cstdlib> (stdlib.h)
- <cstring> (string.h)
- C++11
  <ctgmath> (tgmath.h)
- <ctime> (time.h)
- C++11
  <cuchar> (uchar.h)
- <cwchar> (wchar.h)
- <cwctype> (wctype.h)
Containers:
- C++11
  <array>
- <deque>
- C++11
  <forward_list>
- <list>
- <map>
- <queue>
- <set>
- <stack>
- C++11
  <unordered_map>
- C++11
  <unordered_set>
- <vector>
Input/Output:
- <fstream>
- <iomanip>
- <ios>
- <iosfwd>
- <iostream>
- <istream>
- <ostream>
- <sstream>
- <streambuf>
Multi-threading:
- C++11
  <atomic>
- C++11
  <condition_variable>
- C++11
  <future>
- C++11
  <mutex>
- C++11
  <thread>
Other:
- <algorithm>
- <bitset>
- C++11
  <chrono>
- C++11
  <codecvt>
- <complex>
- <exception>
- <functional>
- C++11
  <initializer_list>
- <iterator>
- <limits>
- <locale>
- <memory>
- <new>
- <numeric>
- C++11
  <random>
- C++11
  <ratio>
- C++11
  <regex>
- <stdexcept>
- <string>
- C++11
  <system_error>
- C++11
  <tuple>
- C++11
  <type_traits>
- C++11
  <typeindex>
- <typeinfo>
- <utility>
- <valarray>

<cmath> (math.h)

functions
- abs
- acos
- C++11
  acosh
- asin
- C++11
  asinh
- atan
- atan2
- C++11
  atanh
- C++11
  cbrt
- ceil
- C++11
  copysign
- cos
- cosh
- C++11
  erf
- C++11
  erfc
- exp
- C++11
  exp2
- C++11
  expm1
- fabs
- C++11
  fdim
- floor
- C++11
  fma
- C++11
  fmax
- C++11
  fmin
- fmod
- C++11
  fpclassify
- frexp
- C++11
  hypot
- C++11
  ilogb
- C++11
  isfinite
- C++11
  isgreater
- C++11
  isgreaterequal
- C++11
  isinf
- C++11
  isless
- C++11
  islessequal
- C++11
  islessgreater
- C++11
  isnan
- C++11
  isnormal
- C++11
  isunordered
- ldexp
- C++11
  lgamma
- C++11
  llrint
- C++11
  llround
- log
- log10
- C++11
  log1p
- C++11
  log2
- C++11
  logb
- C++11
  lrint
- C++11
  lround
- modf
- C++11
  nan
- C++11
  nanf
- C++11
  nanl
- C++11
  nearbyint
- C++11
  nextafter
- C++11
  nexttoward
- pow
- C++11
  remainder
- C++11
  remquo
- C++11
  rint
- C++11
  round
- C++11
  scalbln
- C++11
  scalbn
- C++11
  signbit
- sin
- sinh
- sqrt
- tan
- tanh
- C++11
  tgamma
- C++11
  trunc
macro constants
- HUGE_VAL
- C++11
  HUGE_VALF
- C++11
  HUGE_VALL
- C++11
  INFINITY
- C++11
  math_errhandling
- NAN
types
- C++11
  double_t
- float_t

function

nan

double nan (const char* tagp);

Generate quiet NaN

Returns a quiet NaN (Not-A-Number) value of type double.

The NaN values are used to identify undefined or non-representable values for floating-point elements, such as the square root of negative numbers or the result of 0/0.

The argument can be used by library implementations to distinguish different NaN values in a implementation-specific manner.

Similarly, nanf and nanl return NaN values of type float and long double, respectively.

Parameters

tagp: An implementation-specific C-string.
If this is an empty string (""), the function returns a generic NaN value (the same as returned by passing "NAN" to strtod).

Return Value

A quiet NaN value.

functions

macro constants

types

nan

Parameters

Return Value

See also