Movatterモバイル変換

[0]ホーム
URL:

cppreference.com
Namespaces
Variants
    Actions

      std::signbit

      From cppreference.com
      <cpp‎ |numeric‎ |math
       
       
       
      Common mathematical functions
      Nearest integer floating point operations
      (C++11)(C++11)(C++11)
      (C++11)
      (C++11)
      (C++11)(C++11)(C++11)
      Floating point manipulation functions
      (C++11)(C++11)
      (C++11)
      (C++11)
      Classification and comparison
      (C++11)
      (C++11)
      (C++11)
      (C++11)
      (C++11)
      signbit
      (C++11)
      Types
      (C++11)
      (C++11)
      (C++11)
      Macro constants
       
      Defined in header<cmath>
      (1)
      bool signbit(float num);

      bool signbit(double num);

      bool signbit(longdouble num);
      		(since C++11)
      (until C++23)
      constexprbool signbit(/*floating-point-type*/ num);
      		(since C++23)
      SIMD overload(since C++26)
      Defined in header<simd>
      template</*math-floating-point*/ V>

      constexprtypename/*deduced-simd-t*/<V>::mask_type

        signbit(const V& v_num);
      		 (S)(since C++26)
      Defined in header<cmath>
      template<class Integer>
      bool signbit( Integer num);
      		 (A)(since C++11)
      (constexpr since C++23)
      1) Determines if the given floating point numbernum is negative. The library provides overloads for all cv-unqualified floating-point types as the type of the parameternum.(since C++23)
      S) The SIMD overload performs an element-wisestd::signbit onv_num.
      (Seemath-floating-point anddeduced-simd-t for their definitions.)
      		(since C++26)
      A) Additional overloads are provided for all integer types, which are treated asdouble.

      Contents

      [edit]Parameters

      num - floating-point or integer value
      v_num - a data-parallel object ofstd::basic_simd specialization where its element type is a floating-point type

      [edit]Return value

      1)true ifnum is negative,false otherwise.
      S) A data-parallel mask object where the ith element equalstrue ifv_num[i] is negative orfalse otherwise for alli in the range[​0​, v_num.size()).

      [edit]Notes

      This function detects the sign bit of zeroes, infinities, and NaNs. Along withstd::copysign,std::signbit is one of the only two portable ways to examine the sign of a NaN.

      The additional overloads are not required to be provided exactly as(A). They only need to be sufficient to ensure that for their argumentnum of integer type,std::signbit(num) has the same effect asstd::signbit(static_cast<double>(num)).

      [edit]Example

      Run this code
      #include <cmath>#include <iostream> int main(){std::cout<<std::boolalpha<<"signbit(+0.0) = "<< std::signbit(+0.0)<<'\n'<<"signbit(-0.0) = "<< std::signbit(-0.0)<<'\n'<<"signbit(+nan) = "<< std::signbit(+NAN)<<'\n'<<"signbit(-nan) = "<< std::signbit(-NAN)<<'\n'<<"signbit(+inf) = "<< std::signbit(+INFINITY)<<'\n'<<"signbit(-inf) = "<< std::signbit(-INFINITY)<<'\n';}

      Output:

      signbit(+0.0) = falsesignbit(-0.0) = truesignbit(+nan) = falsesignbit(-nan) = truesignbit(+inf) = falsesignbit(-inf) = true

      [edit]See also

      absolute value of a floating point value (\(\small{|x|}\)|x|)
      (function)[edit]
      (C++11)(C++11)(C++11)
      		 copies the sign of a floating point value
      (function)[edit]
      C documentation forsignbit
      Retrieved from "https://en.cppreference.com/mwiki/index.php?title=cpp/numeric/math/signbit&oldid=149497"
      [8]ページ先頭
      ©2009-2025 Movatter.jp