cpp/thread/promise

1. include<iostream>
2. include<cstdio>
3. include<cmath>

using namespace std;

double function(double x, double y ) {

   return sqrt(x * x + y * y);

} //double(*pt_fun)(double , double) = NULL; //pt_fun = &function;

void arr_fun(double *arr1, double *arr_result, int n ){

   int k = 0;
   for( int i = 0; i < n ; i+=2){
       arr_result[k] = function( arr1[i], arr1[i + 1] );
       k++;
   }

}

int main(){ int n = 8;

double* arr1 = new double [n]; double arr2[] = {1.0 , 1.0 , 2.0, 1.0 , 1.0, 3.0, 3.0, 1.0};

for(int i = 0; i < n; i ++) arr1[i]=arr2[i];

double *a = new double [n / 2]; arr_fun(arr1,a, n ); for ( int i = 0; i < n / 2; i++){

   cout << a[i] << "  ";

} cout << endl;

//OUT: [1.414214 2.236068 3.162278 3.162278]

   delete []a;
   delete []arr1;
   return 0;

}