| Common mathematical functions | |||||||||||||||||||||||||||||||
| Mathematical special functions(C++17) | |||||||||||||||||||||||||||||||
| Mathematical constants(C++20) | |||||||||||||||||||||||||||||||
| Basic linear algebra algorithms(C++26) | |||||||||||||||||||||||||||||||
| Data-parallel types (SIMD)(C++26) | |||||||||||||||||||||||||||||||
| Floating-point environment(C++11) | |||||||||||||||||||||||||||||||
| Complex numbers | |||||||||||||||||||||||||||||||
Numeric array (valarray) | |||||||||||||||||||||||||||||||
| Pseudo-random number generation | |||||||||||||||||||||||||||||||
| Bit manipulation(C++20) | |||||||||||||||||||||||||||||||
| Saturation arithmetic(C++26) | |||||||||||||||||||||||||||||||
| Factor operations | |||||||||||||||||||||||||||||||
|
| ||||||||||||||||||||||||||||||
| Interpolations | |||||||||||||||||||||||||||||||
|
| ||||||||||||||||||||||||||||||
| Generic numeric operations | |||||||||||||||||||||||||||||||
| |||||||||||||||||||||||||||||||
| C-style checked integer arithmetic | |||||||||||||||||||||||||||||||
| |||||||||||||||||||||||||||||||
| Nearest integer floating point operations | |||||||||||||||||||||||||||||||||||||||||
|
| ||||||||||||||||||||||||||||||||||||||||
| Floating point manipulation functions | |||||||||||||||||||||||||||||||||||||||||
|
| ||||||||||||||||||||||||||||||||||||||||
| Classification and comparison | |||||||||||||||||||||||||||||||||||||||||
| |||||||||||||||||||||||||||||||||||||||||
| Types | |||||||||||||||||||||||||||||||||||||||||
| Macro constants | |||||||||||||||||||||||||||||||||||||||||
|
| ||||||||||||||||||||||||||||||||||||||||
Defined in header <cmath> | ||
| (1) | ||
float modf(float num,float* iptr); double modf(double num,double* iptr); | (until C++23) | |
constexpr/* floating-point-type */ modf(/* floating-point-type */ num, | (since C++23) | |
float modff(float num,float* iptr); | (2) | (since C++11) (constexpr since C++23) |
longdouble modfl(longdouble num,longdouble* iptr); | (3) | (since C++11) (constexpr since C++23) |
Additional overloads(since C++11) | ||
Defined in header <cmath> | ||
template<class Integer> double modf( Integer num,double* iptr); | (A) | (constexpr since C++23) |
std::modf for all cv-unqualified floating-point types as the type of the parameternum and the pointed-to type ofiptr.(since C++23)A) Additional overloads are provided for all integer types, which are treated asdouble. | (since C++11) |
Contents |
| num | - | floating-point or integer value |
| iptr | - | pointer to floating-point value to store the integral part to |
If no errors occur, returns the fractional part ofnum with the same sign asnum. The integral part is put into the value pointed to byiptr.
The sum of the returned value and the value stored in*iptr givesnum (allowing for rounding).
This function is not subject to any errors specified inmath_errhandling.
If the implementation supports IEEE floating-point arithmetic (IEC 60559),
This function behaves as if implemented as follows:
double modf(double num,double* iptr){#pragma STDC FENV_ACCESS ONint save_round=std::fegetround();std::fesetround(FE_TOWARDZERO);*iptr=std::nearbyint(num);std::fesetround(save_round);returnstd::copysign(std::isinf(num)?0.0: num-(*iptr), num);}
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::modf(num, iptr) has the same effect asstd::modf(static_cast<double>(num), iptr).
Compares different floating-point decomposition functions:
#include <cmath>#include <iostream>#include <limits> int main(){double f=123.45;std::cout<<"Given the number "<< f<<" or "<<std::hexfloat<< f<<std::defaultfloat<<" in hex,\n"; double f3;double f2= std::modf(f,&f3);std::cout<<"modf() makes "<< f3<<" + "<< f2<<'\n'; int i; f2=std::frexp(f,&i);std::cout<<"frexp() makes "<< f2<<" * 2^"<< i<<'\n'; i=std::ilogb(f);std::cout<<"logb()/ilogb() make "<< f/std::scalbn(1.0, i)<<" * "<<std::numeric_limits<double>::radix<<"^"<<std::ilogb(f)<<'\n'; // special values f2= std::modf(-0.0,&f3);std::cout<<"modf(-0) makes "<< f3<<" + "<< f2<<'\n'; f2= std::modf(-INFINITY,&f3);std::cout<<"modf(-Inf) makes "<< f3<<" + "<< f2<<'\n';}
Possible output:
Given the number 123.45 or 0x1.edccccccccccdp+6 in hex,modf() makes 123 + 0.45frexp() makes 0.964453 * 2^7logb()/ilogb() make 1.92891 * 2^6modf(-0) makes -0 + -0modf(-Inf) makes -INF + -0
(C++11)(C++11)(C++11) | nearest integer not greater in magnitude than the given value (function)[edit] |
C documentation formodf | |
