UU_la_parallel_programming_practical_assignments/cpp_template/calc.cpp

#include <math.h>
 
// Get the Square root of a number. 
double squareRoot(const double a) 
    {
    double b = sqrt(a);
    if(b != b) // NaN check
        { return -1.0; }
    else
        { return sqrt(a); }
    }