# std::sqrt(std::valarray)

< cpp‎ | numeric‎ | valarray
(diff) ← Older revision | Latest revision (diff) | Newer revision → (diff)
 Defined in header `` template< class T > valarray sqrt( const valarray& va );

For each element in `va` computes the square root of the value of the element.

## Contents

### Parameters

 va - value array to apply the operation to

### Return value

Value array containing square roots of the values in `va`.

### Notes

Unqualified function (sqrt) is used to perform the computation. If such function is not available, std::sqrt is used due to argument dependent lookup.

The function can be implemented with the return type different from std::valarray. In this case, the replacement type has the following properties:

### Possible implementation

 ```template valarray sqrt(const valarray& va) { valarray other = va; for (T &i : other) { i = sqrt(i); } return other; }```

### Example

Finds real roots of multiple quadratic equations.

```#include <valarray>
#include <iostream>

int main()
{
std::valarray<double> a(1, 8);
std::valarray<double> b{1, 2, 3, 4, 5, 6, 7, 8};
std::valarray<double> c = -b;
// literals must also be of type T (double in this case)
std::valarray<double> d = std::sqrt((b * b - 4.0 * a * c));
std::valarray<double> x1 = (-b - d) / (2.0 * a);
std::valarray<double> x2 = (-b + d) / (2.0 * a);
std::cout << "quadratic equation    root 1,  root 2" << "\n";
for (size_t i = 0; i < a.size(); ++i) {
std::cout << a[i] << "x\u00B2 + " << b[i] << "x + " << c[i] << " = 0   ";
std::cout << x1[i] << ", " << x2[i] << "\n";
}
}```

Output:

```quadratic equation    root 1,  root 2
1x² + 1x + -1 = 0   -1.61803, 0.618034
1x² + 2x + -2 = 0   -2.73205, 0.732051
1x² + 3x + -3 = 0   -3.79129, 0.791288
1x² + 4x + -4 = 0   -4.82843, 0.828427
1x² + 5x + -5 = 0   -5.8541, 0.854102
1x² + 6x + -6 = 0   -6.87298, 0.872983
1x² + 7x + -7 = 0   -7.88748, 0.887482
1x² + 8x + -8 = 0   -8.89898, 0.898979```