# ldexp

## PROLOG



           This manual page is part of the POSIX Programmer's Manual.  The
           Linux implementation of this interface may differ (consult the
           corresponding Linux manual page for details of Linux behavior), or
           the interface may not be implemented on Linux.
    


## NAME



           ldexp, ldexpf, ldexpl — load exponent of a floating-point number
    


## SYNOPSIS



           #include <math.h>
    
           double ldexp(double _x_ , int _exp_);
           float ldexpf(float _x_ , int _exp_);
           long double ldexpl(long double _x_ , int _exp_);
    


## DESCRIPTION



           The functionality described on this reference page is aligned with
           the ISO C standard. Any conflict between the requirements
           described here and the ISO C standard is unintentional. This
           volume of POSIX.1‐2017 defers to the ISO C standard.
    
           These functions shall compute the quantity _x_ * 2 _exp_.
    
           An application wishing to check for error situations should set
           _errno_ to zero and call _feclearexcept_(FE_ALL_EXCEPT) before calling
           these functions. On return, if _errno_ is non-zero or
           _fetestexcept_(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW |
           FE_UNDERFLOW) is non-zero, an error has occurred.
    


## RETURN VALUE



           Upon successful completion, these functions shall return _x_
           multiplied by 2, raised to the power _exp_.
    
           If these functions would cause overflow, a range error shall occur
           and _ldexp_(), _ldexpf_(), and _ldexpl_() shall return ±HUGE_VAL,
           ±HUGE_VALF, and ±HUGE_VALL (according to the sign of _x_),
           respectively.
    
           If the correct value would cause underflow, and is not
           representable, a range error may occur, and _ldexp_(), _ldexpf_(), and
           _ldexpl_() shall return 0.0, or (if IEC 60559 Floating-Point is not
           supported) an implementation-defined value no greater in magnitude
           than DBL_MIN, FLT_MIN, and LDBL_MIN, respectively.
    
           If _x_ is NaN, a NaN shall be returned.
    
           If _x_ is ±0 or ±Inf, _x_ shall be returned.
    
           If _exp_ is 0, _x_ shall be returned.
    
           If the correct value would cause underflow, and is representable,
           a range error may occur and the correct value shall be returned.
    


## ERRORS



           These functions shall fail if:
    
           Range Error The result overflows.
    
                       If the integer expression (_math_errhandling_ &
                       MATH_ERRNO) is non-zero, then _errno_ shall be set to
                       **[ERANGE]**.  If the integer expression (_math_errhandling_
                       & MATH_ERREXCEPT) is non-zero, then the overflow
                       floating-point exception shall be raised.
    
           These functions may fail if:
    
           Range Error The result underflows.
    
                       If the integer expression (_math_errhandling_ &
                       MATH_ERRNO) is non-zero, then _errno_ shall be set to
                       **[ERANGE]**.  If the integer expression (_math_errhandling_
                       & MATH_ERREXCEPT) is non-zero, then the underflow
                       floating-point exception shall be raised.
    
           _The following sections are informative._
    


## EXAMPLES



           None.
    


## APPLICATION USAGE



           On error, the expressions (_math_errhandling_ & MATH_ERRNO) and
           (_math_errhandling_ & MATH_ERREXCEPT) are independent of each other,
           but at least one of them must be non-zero.
    


## RATIONALE



           None.
    


## FUTURE DIRECTIONS



           None.
    


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