Movatterモバイル変換

[0]ホーム
URL:

cppreference.com
Namespaces
Variants
    Actions

      std::copysign,std::copysignf,std::copysignl

      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)
      (C++11)(C++11)
      copysign
      (C++11)
      Classification and comparison
      (C++11)
      (C++11)
      (C++11)
      (C++11)
      (C++11)
      (C++11)
      Types
      (C++11)
      (C++11)
      (C++11)
      Macro constants
       
      Defined in header<cmath>
      (1)
      float       copysign(float mag,float sgn);

      double      copysign(double mag,double sgn);

      longdouble copysign(longdouble mag,longdouble sgn);
      		(until C++23)
      constexpr/*floating-point-type*/

                  copysign(/*floating-point-type*/ mag,

                             /*floating-point-type*/ sgn);
      		(since C++23)
      float       copysignf(float mag,float sgn);
      		 (2)(since C++11)
      (constexpr since C++23)
      longdouble copysignl(longdouble mag,longdouble sgn);
      		 (3)(since C++11)
      (constexpr since C++23)
      SIMD overload(since C++26)
      Defined in header<simd>
      template<class V0,class V1>

      constexpr/*math-common-simd-t*/<V0, V1>

                  copysign(const V0& v_mag,const V1& v_sgn);
      		 (S)(since C++26)
      Defined in header<cmath>
      template<class Integer>
      double      copysign( Integer mag, Integer sgn);
      		 (A)(constexpr since C++23)
      1-3) Composes a floating point value with the magnitude ofmag and the sign ofsgn. The library provides overloads ofstd::copysign for all cv-unqualified floating-point types as the type of the parameters.(since C++23)
      S) The SIMD overload performs an element-wisestd::copysign onv_magandv_sgn.
      (Seemath-common-simd-t for its definition.)
      		(since C++26)
      A) Additional overloads are provided for all integer types, which are treated asdouble.
      		(since C++11)

      Contents

      [edit]Parameters

      mag, sgn - floating-point or integer values

      [edit]Return value

      If no errors occur, the floating point value with the magnitude ofmag and the sign ofsgn is returned.

      Ifmag is NaN, then NaN with the sign ofsgn is returned.

      Ifsgn is -0, the result is only negative if the implementation supports the signed zero consistently in arithmetic operations.

      [edit]Error handling

      This function is not subject to any errors specified inmath_errhandling.

      If the implementation supports IEEE floating-point arithmetic (IEC 60559),

      [edit]Notes

      std::copysign is the only portable way to manipulate the sign of a NaN value (to examine the sign of a NaN,std::signbit may also be used).

      The additional overloads are not required to be provided exactly as(A). They only need to be sufficient to ensure that for their first argumentnum1 and second argumentnum2:

      • Ifnum1 ornum2 has typelongdouble, thenstd::copysign(num1, num2) has the same effect asstd::copysign(static_cast<longdouble>(num1),
                     static_cast<longdouble>(num2))        .
      • Otherwise, ifnum1 and/ornum2 has typedouble or an integer type, thenstd::copysign(num1, num2) has the same effect asstd::copysign(static_cast<double>(num1),
                     static_cast<double>(num2))        .
      • Otherwise, ifnum1 ornum2 has typefloat, thenstd::copysign(num1, num2) has the same effect asstd::copysign(static_cast<float>(num1),
                     static_cast<float>(num2))        .
      		(until C++23)

      Ifnum1 andnum2 have arithmetic types, thenstd::copysign(num1, num2) has the same effect asstd::copysign(static_cast</*common-floating-point-type*/>(num1),
                   static_cast</*common-floating-point-type*/>(num2))      , where/*common-floating-point-type*/ is the floating-point type with the greatestfloating-point conversion rank and greatestfloating-point conversion subrank between the types ofnum1 andnum2, arguments of integer type are considered to have the same floating-point conversion rank asdouble.

      If no such floating-point type with the greatest rank and subrank exists, thenoverload resolution does not result in a usable candidate from the overloads provided.

      		(since C++23)

      [edit]Example

      Run this code
      #include <cmath>#include <iostream> int main(){std::cout<<std::showpos<<"copysign(1.0,+2.0) = "<< std::copysign(1.0,+2.0)<<'\n'<<"copysign(1.0,-2.0) = "<< std::copysign(1.0,-2.0)<<'\n'<<"copysign(inf,-2.0) = "<< std::copysign(INFINITY,-2.0)<<'\n'<<"copysign(NaN,-2.0) = "<< std::copysign(NAN,-2.0)<<'\n';}

      Output:

      copysign(1.0,+2.0) = +1copysign(1.0,-2.0) = -1copysign(inf,-2.0) = -infcopysign(NaN,-2.0) = -nan

      [edit]See also

      absolute value of a floating point value (\(\small{|x|}\)|x|)
      (function)[edit]
      (C++11)
      		 checks if the given number is negative
      (function)[edit]
      C documentation forcopysign
      Retrieved from "https://en.cppreference.com/mwiki/index.php?title=cpp/numeric/math/copysign&oldid=154248"
      [8]ページ先頭
      ©2009-2025 Movatter.jp