c++ - vector in function - how to do return

Well, you are trying to return a vector as strings. This won't work because they are different types and have no conversion defined from one to the other. Your function has the return type string.

Solution 1

In your case you could append the lines to a string instead of adding them to a vector? You are using the result as a string anyhow.

You could change seqs to string and append data to it with the += operator.

Solution 2

You could also change the return type to vector but you would need to loop over the items and print them instead in your main.

vector getseq(char * db_file)
{
    ...
    return seqs;

}

Caveat Lector: this will copy all the items. If you want to avoid this pass the vector as a reference to the function and add to it.

Looping is quite easy using iterators:

// Get the strings as a vector. 
vector seqs = getseq(argv[1]);


// This is just a matter of taste, we create an alias for the vector iterator type.
typedef vector:iterator_t string_iter;

// Loop till we hit the end of the vector.
for (string_iter i = seqs.begin(); i != seqs.end(); i++)
{
   cout << *i; // you could add endlines, commas here etc.
}

---

If you want to avoid copying a vector and all the strings make getseq take a reference to a vector.

void getseq(char * db_file, vector &seqs)
{
    ...
    // vector seqs; this line is not needed anymore.

    ...

    // we don't need to return anything anymore
}

You would then need to create the vector in your main instead, making my above code:

// Get the strings as a vector. 
vector seqs;   // Holds our strings.
getseq(argv[1], seqs); // We don't return anything.


// This is just a matter of taste, we create an alias for the vector iterator type.
typedef vector:iterator_t string_iter;

// Print prelude.
cout << "Sekwencje: \n";

// Loop till we hit the end of the vector.
for (string_iter i = seqs.begin(); i != seqs.end(); i++)
{
   cout << *i << " "; // Do processing, add endlines, commas here etc.

}

cout << endl;

---

Edit after comments

int main(int argc, char * argv[1])

{
    // This is what you need, sorry for the confusion. 
    // This copies the vector returned to seqs
    vector seqs = getseq(argv[1]); 

    // This is just a matter of taste, we create an alias for the vector iterator type.
    typedef vector::iterator string_iter;

    // Print prelude.
    cout << "Sekwencje: \n";


    // Loop till we hit the end of the vector.
    for (string_iter i = seqs.begin(); i != seqs.end(); i++)
    {
        cout << *i << " "; // Do processing, add endlines, commas here etc.
    }

    cout << endl;
}