SQRT

Section: POSIX Programmer's Manual (3P)
Updated: 2003
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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

sqrt, sqrtf, sqrtl - square root function  

SYNOPSIS

#include <math.h>

double sqrt(double x);
float sqrtf(float x);
long double sqrtl(long double x);
 

DESCRIPTION

These functions shall compute the square root of their argument x, sqrt(x).

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 square root of x.

For finite values of x < -0, a domain error shall occur, and  either a NaN (if supported), or an implementation-defined value shall be returned.

If x is NaN, a NaN shall be returned.

If x is ±0 or +Inf, x shall be returned.

If x is -Inf, a domain error shall occur, and either a NaN (if supported), or an implementation-defined value shall be returned.  

ERRORS

These functions shall fail if:

Domain Error
The finite value of x is < -0, or x is -Inf.

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

 

Taking the Square Root of 9.0


#include <math.h>
...
double x = 9.0;
double result;
...
result = sqrt(x);
 

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.  

SEE ALSO

feclearexcept(), fetestexcept(), isnan(), the Base Definitions volume of IEEE Std 1003.1-2001, Section 4.18, Treatment of Error Conditions for Mathematical Functions, <math.h>, <stdio.h>  

COPYRIGHT

Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html .