sqrt, sqrtf, sqrtl
| Defined in header <math.h>
|
||
| float sqrtf( float arg ); |
(1) | (since C99) |
| double sqrt( double arg ); |
(2) | |
| long double sqrtl( long double arg ); |
(3) | (since C99) |
| Defined in header <tgmath.h>
|
||
| #define sqrt( arg ) |
(4) | (since C99) |
arg.arg has type long double, sqrtl is called. Otherwise, if arg has integer type or the type double, sqrt is called. Otherwise, sqrtf is called. If arg is complex or imaginary, then the macro invokes the corresponding complex function (csqrtf, csqrt, csqrtl).Contents |
[edit] Parameters
| arg | - | floating point value |
[edit] Return value
If no errors occur, square root of arg (√arg), is returned.
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 (after rounding) is returned.
[edit] Error handling
Errors are reported as specified in math_errhandling.
Domain error occurs if arg is less than zero.
If the implementation supports IEEE floating-point arithmetic (IEC 60559),
- If the argument is less than -0, FE_INVALID is raised and NaN is returned.
- If the argument is +∞ or ±0, it is returned, unmodified.
- If the argument is NaN, NaN is returned
[edit] Notes
sqrt is required by the IEEE standard to be exact. The only other operations required to be exact are the arithmetic operators and the function fma. After rounding to the return type (using default rounding mode), the result of sqrt is indistinguishable from the infinitely precise result. In other words, the error is less than 0.5 ulp. Other functions, including pow, are not so constrained.
[edit] Example
#include <stdio.h> #include <math.h> #include <errno.h> #include <fenv.h> #pragma STDC FENV_ACCESS ON int main(void) { // normal use printf("sqrt(100) = %f\n", sqrt(100)); printf("sqrt(2) = %f\n", sqrt(2)); printf("golden ratio = %f\n", (1+sqrt(5))/2); // special values printf("sqrt(-0) = %f\n", sqrt(-0.0)); // error handling errno = 0; feclearexcept(FE_ALL_EXCEPT); printf("sqrt(-1.0) = %f\n", sqrt(-1)); if(errno == EDOM) perror(" errno == EDOM"); if(fetestexcept(FE_INVALID)) puts(" FE_INVALID was raised"); }
Possible output:
sqrt(100) = 10.000000
sqrt(2) = 1.414214
golden ratio = 1.618034
sqrt(-0) = -0.000000
sqrt(-1.0) = -nan
errno = EDOM: Numerical argument out of domain
FE_INVALID was raised[edit] References
- C11 standard (ISO/IEC 9899:2011):
- 7.12.7.5 The sqrt functions (p: 249)
- 7.25 Type-generic math <tgmath.h> (p: 373-375)
- F.10.4.5 The sqrt functions (p: 525)
- C99 standard (ISO/IEC 9899:1999):
- 7.12.7.5 The sqrt functions (p: 229-230)
- 7.22 Type-generic math <tgmath.h> (p: 335-337)
- F.9.4.5 The sqrt functions (p: 462)
- C89/C90 standard (ISO/IEC 9899:1990):
- 4.5.5.2 The sqrt function
[edit] See also
| (C99)(C99) |
computes a number raised to the given power (xy) (function) |
| (C99)(C99)(C99) |
computes cubic root (3√x) (function) |
| (C99)(C99)(C99) |
computes square root of the sum of the squares of two given numbers (√x2 +y2 ) (function) |
| (C99)(C99)(C99) |
computes the complex square root (function) |
| C++ documentation for sqrt
| |
