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      std::remquo,std::remquof,std::remquol

      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)
      (C++11)
      Types
      (C++11)
      (C++11)
      (C++11)
      Macro constants
       
      Defined in header<cmath>
      (1)
      float       remquo(float x,float y,int* quo);

      double      remquo(double x,double y,int* quo);

      longdouble remquo(longdouble x,longdouble y,int* quo);
      (since C++11)
      (until C++23)
      constexpr/* floating-point-type */

                  remquo(/* floating-point-type */ x,

                           /* floating-point-type */ y,int* quo);
      (since C++23)
      float       remquof(float x,float y,int* quo);
      (2)(since C++11)
      (constexpr since C++23)
      longdouble remquol(longdouble x,longdouble y,int* quo);
      (3)(since C++11)
      (constexpr since C++23)
      Defined in header<cmath>
      template<class Arithmetic1,class Arithmetic2>

      /* common-floating-point-type */

          remquo( Arithmetic1 x, Arithmetic2 y,int* quo);
      (A)(since C++11)
      (constexpr since C++23)
      1-3) Computes the floating-point remainder of the division operationx/ y as thestd::remainder() function does. Additionally, the sign and at least the three of the last bits ofx/ y will be stored inquo, sufficient to determine the octant of the result within a period. The library provides overloads ofstd::remquo for all cv-unqualified floating-point types as the type of the parametersx andy.(since C++23)
      A) Additional overloads are provided for all other combinations of arithmetic types.

      Contents

      [edit]Parameters

      x, y - floating-point or integer values
      quo - pointer toint to store the sign and some bits ofx/ y

      [edit]Return value

      If successful, returns the floating-point remainder of the divisionx/ y as defined instd::remainder, and stores, in*quo, the sign and at least three of the least significant bits ofx/ y (formally, stores a value whose sign is the sign ofx/ y and whose magnitude is congruentmodulo 2n
      to the magnitude of the integral quotient ofx/ y, wheren is an implementation-defined integer greater than or equal to3).

      Ify is zero, the value stored in*quo is unspecified.

      If a domain error occurs, an implementation-defined value is returned (NaN where supported).

      If a range error occurs due to underflow, the correct result is returned if subnormals are supported.

      Ify is zero, but the domain error does not occur, zero is returned.

      [edit]Error handling

      Errors are reported as specified inmath_errhandling.

      Domain error may occur ify is zero.

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

      • The currentrounding mode has no effect.
      • FE_INEXACT is never raised.
      • Ifx is ±∞ andy is not NaN, NaN is returned andFE_INVALID is raised.
      • Ify is ±0 andx is not NaN, NaN is returned andFE_INVALID is raised.
      • If eitherx ory is NaN, NaN is returned.

      [edit]Notes

      POSIX requires that a domain error occurs ifx is infinite ory is zero.

      This function is useful when implementing periodic functions with the period exactly representable as a floating-point value: when calculatingsin(πx) for a very largex, callingstd::sin directly may result in a large error, but if the function argument is first reduced withstd::remquo, the low-order bits of the quotient may be used to determine the sign and the octant of the result within the period, while the remainder may be used to calculate the value with high precision.

      On some platforms this operation is supported by hardware (and, for example, on Intel CPUs,FPREM1 leaves exactly 3 bits of precision in the quotient when complete).

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

      Ifnum1 andnum2 have arithmetic types, thenstd::remquo(num1, num2, quo) has the same effect asstd::remquo(static_cast</*common-floating-point-type*/>(num1),
                 static_cast</*common-floating-point-type*/>(num2), quo)
      , 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 <cfenv>#include <cmath>#include <iostream> #ifndef __GNUC__#pragma STDC FENV_ACCESS ON#endif constdouble pi=std::acos(-1);// or std::numbers::pi since C++20 double cos_pi_x_naive(double x){returnstd::cos(pi* x);} // the period is 2, values are (0;0.5) positive, (0.5;1.5) negative, (1.5,2) positivedouble cos_pi_x_smart(double x){int quadrant;double rem= std::remquo(x,1,&quadrant);    quadrant=static_cast<unsigned>(quadrant)%2;// The period is 2.return quadrant==0?std::cos(pi* rem):-std::cos(pi* rem);} int main(){std::cout<<std::showpos<<"naive:\n"<<"  cos(pi * 0.25) = "<< cos_pi_x_naive(0.25)<<'\n'<<"  cos(pi * 1.25) = "<< cos_pi_x_naive(1.25)<<'\n'<<"  cos(pi * 2.25) = "<< cos_pi_x_naive(2.25)<<'\n'<<"smart:\n"<<"  cos(pi * 0.25) = "<< cos_pi_x_smart(0.25)<<'\n'<<"  cos(pi * 1.25) = "<< cos_pi_x_smart(1.25)<<'\n'<<"  cos(pi * 2.25) = "<< cos_pi_x_smart(2.25)<<'\n'<<"naive:\n"<<"  cos(pi * 1000000000000.25) = "<< cos_pi_x_naive(1000000000000.25)<<'\n'<<"  cos(pi * 1000000000001.25) = "<< cos_pi_x_naive(1000000000001.25)<<'\n'<<"smart:\n"<<"  cos(pi * 1000000000000.25) = "<< cos_pi_x_smart(1000000000000.25)<<'\n'<<"  cos(pi * 1000000000001.25) = "<< cos_pi_x_smart(1000000000001.25)<<'\n'; // error handlingstd::feclearexcept(FE_ALL_EXCEPT); int quo;std::cout<<"remquo(+Inf, 1) = "<< std::remquo(INFINITY,1,&quo)<<'\n';if(fetestexcept(FE_INVALID))std::cout<<"  FE_INVALID raised\n";}

      Possible output:

      naive:  cos(pi * 0.25) = +0.707107  cos(pi * 1.25) = -0.707107  cos(pi * 2.25) = +0.707107smart:  cos(pi * 0.25) = +0.707107  cos(pi * 1.25) = -0.707107  cos(pi * 2.25) = +0.707107naive:  cos(pi * 1000000000000.25) = +0.707123  cos(pi * 1000000000001.25) = -0.707117smart:  cos(pi * 1000000000000.25) = +0.707107  cos(pi * 1000000000001.25) = -0.707107remquo(+Inf, 1) = -nan  FE_INVALID raised

      [edit]See also

      computes quotient and remainder of integer division
      (function)[edit]
      (C++11)(C++11)
      remainder of the floating point division operation
      (function)[edit]
      (C++11)(C++11)(C++11)
      signed remainder of the division operation
      (function)[edit]
      C documentation forremquo
      Retrieved from "https://en.cppreference.com/mwiki/index.php?title=cpp/numeric/math/remquo&oldid=181909"

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