Nrthugu

I would like to create an array i_array with 15 elements and rate every element with formula

a = sin((Pi * (i - 7)) / 15)

and return it.

#include <cmath>

#include <cstddef>

#include <iostream>



void sinuss(double (&arr)[15]) {

    for (int i = 0; i < 15; ++i) {

        arr[i] = std::sin((M_PI * (i - 7)) / 15);

        std::cout << arr[i] << ' ';

    }

    std::cout << 'n';

}



void modBinSearch(double arr, double start, double end){





    if (start > end){

        return -1;

    }

    const int mitte = start +((end-start)/2);

    if(arr[mitte] == 0.0){

        return mitte;

    }

    else if(arr[mitte] > 0.0){

           return modBinSearch(arr, start, mitte-1);

        }

    return modBinSearch(arr, mitte+1,end);





}



int main() {

    double i_array[15];

    sinuss(i_array);

    for (int i = 0; i < 15; ++i) {

        std::cout << i_array[i] << ' ';

    }

    std::cout << 'n';



    int arr = sinuss(i_array);

    int n = sizeof(arr)/sizeof(arr[0]);

    int result = modBinSearch(arr, 0, n-1);

    return 0;

}

I have no idea. I don't know what my error is.

I am new in C++, because it I have a lot of problem with it:(

In my function sinuss() I should return rated elements as array and in function modBinSearch() I should return the least element who not smaller as 0.0 is. But my programm is wrong :(

Define a type of what you desire. Suggesting a std::array<double,15>. It makes coding what you want more natural.

    #include <array>

    #include <iostream>

    #include <cmath>



    using namespace std;



    using ArrOf15Dbl = array<double, 15>;



    ArrOf15Dbl sinuss() {

        ArrOf15Dbl i_array;



        for (int i = 0; i < 15; ++i) {



            i_array[i] = sin((M_PI * (i - 7)) / 15);

            cout << i_array[i] << ' ';

        }

        cout << 'n';

        return i_array;

    }



    int main() {

        ArrOf15Dbl x = sinuss();

        for (auto i : x) {

            cout << i << ' ';

        }

        cout << 'n';

    }

But returning arrays from a function is not possible with C++98/03. So one solution is to allocate the needed memory dynamically, but don't forget to release it later!

    #include <cmath>

    #include <cstddef>

    #include <iostream>



    int const kArrSiz = 15;



    // OBS: caller assumes ownership of array pointer!

    // Must be deleted with "delete  foobar;"

    double* sinuss() {

        double* i_array = new double[kArrSiz];



        for (int i = 0; i < kArrSiz; ++i) {



            i_array[i] = std::sin((M_PI * (i - 7)) / kArrSiz);

            std::cout << i_array[i] << ' ';

        }

        std::cout << 'n';

        return i_array;

    }



    int main() {

        double* x = sinuss();

        for (int i  = 0; i < kArrSiz; ++i) {

            std::cout << x[i] << ' ';

        }

        std::cout << 'n';

        delete  x;

        return EXIT_SUCCESS;

    }

But with a change of interface to your function, it can be made safer by requiring the caller to allocate the array and your function instead fills it with your required values.

    void sinuss(double (&arr)[15]) {

        for (int i = 0; i < 15; ++i) {

            arr[i] = std::sin((M_PI * (i - 7)) / 15);

            std::cout << arr[i] << ' ';

        }

        std::cout << 'n';

    }



    int main() {

        double i_array[15];

        sinuss(i_array);

        for (int i = 0; i < 15; ++i) {

            std::cout << i_array[i] << ' ';

        }

        std::cout << 'n';

        return EXIT_SUCCESS;

    }

There are usually better ways to write loops that use a sequence of floating-point values, such as using an integer for loop control and calculating the floating-point value from the integer in each iteration. (Alternatively, you can use a floating-point object for loop control but take care to use only integer values for the loop expressions.)