Listing 8.1 - Compile and runtime fixes

[ITHelpDec]

PR in response to issue #39.

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In order for this code to run, we must perform the following commits and amend listing 6.1 to return an empty shared pointer at line 37 instead of throwing.

// if(data.empty()) throw empty_stack();
if(data.empty()) return std::shared_ptr<T>();

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Tested with a simple list of ints, but will investigate with larger containers of varying types to benchmark speed comparisons.

Test case - (click to expand / collapse)

template <typename T>
void print_list(const std::list<T> &il) {
    for (auto &&e : il) {
        std::cout << e << ' ';
    } std::cout << '\n';
}

int main()
{
    std::list<int> il = { 1, 4, 5, 3, 6, 7, 4 };
    print_list(il);
    
    auto sorted_il = parallel_quick_sort(il);
    print_list(sorted_il);
    
    return 0;
}

// 1 4 5 3 6 7 4 
// 1 3 4 4 5 6 7 
// Program ended with exit code: 0

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I'm attempting to try implement the same sorter with our lock-free stack, but issues exist in all of the implementations provided in chapter 7, and boost is showing data races with Thread Sanitiser, so I'll come back to this when I know where to start.

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A relatively simple fix, but it would just be nice if it worked out of the box instead of having to correct it.