Question

Is this possible? According to what I’m trying to accomplish, it appears not so.

The function

static std::string str_repeat(std::string * str, int num_times) {

    std::string * str_rep = new std::string;

    for (int n = 1; n <= num_times; n++) {
        str_rep = str_rep + str;
    }

    std::string ret = *str_rep; //error

    delete str;
    delete str_rep;

    return ret;
}

Update

Sorry, I didn’t post the error in the first place because I thought it was a universal C++ issue that I was doing wrong. Here it is.

error: invalid operands of types ‘std::string* {aka std::basic_string<char>*}’ and ‘std::string* {aka std::basic_string<char>*}’ to binary ‘operator+’

Answer 1

You are trying to add two pointers together, which is why it wont compile. Don’t forget that a pointer is a memory address, the +operator wont be called in your example – you would have to dereference the pointer, but I wouldn’t recommend that pattern in this case. I’d suggest you read up a little more about pointers and references 🙂

Be very careful about when you delete memory. It’s bad practice to delete memory away from the context in which it was allocated – that’s a recipe for bugs. Also, if you allocated on the stack before calling ‘delete str’, your application would likely crash.

For string manipulation I would really recommend passing by const reference. Thus will will deal with memory allocation for you, as you can pass std::string by value, and it will internally perform memory allocation as needed…

Another couple of points.
In C, languages, we usually count from ‘0’, so I would change your for loop
In a proper application, I would have some debug assert on your input parameters: i.e. you should assert that num_times is ‘>0’

The following code compiles and executes with result “barbarbar”…

Cheers and good luck,
Jon

#include <string>
#include <iostream>

using namespace std;

static string str_repeat(const string& str, int count)
{
    string returnData;

    for (int n = 0; n < count; n++)
    {
        returnData.append(str);
    }

    return returnData;
}

int main(int argc, char* argv[])
{
    string foo = "bar";

    string duplicated = str_repeat(foo, 3);

    cout << duplicated;

    return 0;
}