### _fsqrt -- Calculate Square Root

Format

>     #include <builtin.h>
>     double _fsqrt(double x);

Language Level: Extension
_fsqrt computes the square root of x using the FSQRT 80387 instruction. Note that this function does not set errno as the sqrt function does. If you pass a negative value to this function, an exception is generated.

Note: _fsqrt is a built-in function, which means it is implemented as an inline instruction and has no backing code in the library. For this reason:

- You cannot take the address of _fsqrt.
- You cannot parenthesize a call to _fsqrt. (Parentheses specify a call to the function's backing code, and _fsqrt has none.)

Return Value
_fsqrt returns the value of the square root of x.

Example
This example calculates the square root of 4.

    #include <builtin.h>
    #include <stdio.h>

    int main(void)
    {
       double x;

       x = 4.0;
       printf("The square root of %lf is %lf.\n", x, _fsqrt(x));
       return 0;

       /********************************************************
          The output should be:

          The square root of 4.000000 is 2.000000.
       ********************************************************/
    }

sqrt -- Calculate Square Root
<math.h>