# lround

## 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



           lround, lroundf, lroundl — round to nearest integer value
    


## SYNOPSIS



           #include <math.h>
    
           long lround(double _x_);
           long lroundf(float _x_);
           long lroundl(long double _x_);
    


## 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 round their argument to the nearest integer
           value, rounding halfway cases away from zero, regardless of the
           current rounding direction.
    
           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 the
           rounded integer value.
    
           If _x_ is NaN, a domain error shall occur and an unspecified value
           is returned.
    
           If _x_ is +Inf, a domain error shall occur and an unspecified value
           is returned.
    
           If _x_ is -Inf, a domain error shall occur and an unspecified value
           is returned.
    
           If the correct value is positive and too large to represent as a
           **long** , an unspecified value shall be returned.  On systems that
           support the IEC 60559 Floating-Point option, a domain shall occur;
           otherwise, a domain error may occur.
    
           If the correct value is negative and too large to represent as a
           **long** , an unspecified value shall be returned.  On systems that
           support the IEC 60559 Floating-Point option, a domain shall occur;
           otherwise, a domain error may occur.
    


## ERRORS



           These functions shall fail if:
    
           Domain Error
                       The _x_ argument is NaN or ±Inf, or the correct value is
                       not representable as an integer.
    
                       If the integer expression (_math_errhandling_ &
                       MATH_ERRNO) is non-zero, then _errno_ shall be set to
                       **[EDOM]**.  If the integer expression (_math_errhandling_ &
                       MATH_ERREXCEPT) is non-zero, then the invalid
                       floating-point exception shall be raised.
    
           These functions may fail if:
    
           Domain Error
                       The correct value is not representable as an integer.
    
                       If the integer expression (_math_errhandling_ &
                       MATH_ERRNO) is non-zero, then _errno_ shall be set to
                       **[EDOM]**.  If the integer expression (_math_errhandling_ &
                       MATH_ERREXCEPT) is non-zero, then the invalid
                       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



           These functions differ from the _lrint_() functions in the default
           rounding direction, with the _lround_() functions rounding halfway
           cases away from zero and needing not to raise the inexact
           floating-point exception for non-integer arguments that round to
           within the range of the return type.
    


## FUTURE DIRECTIONS



           None.
    


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