Why Does `std::sort` Fail to Sort a `std::list` of Structures?

Sorting a List with STL Sort Function: An Implementation Issue

When attempting to sort a list of structures using the std::sort function, you may encounter a compilation error indicating a missing operator-. This error arises when the supplied comparator, SortDescending, operates on elements of a std::list, which supports bidirectional iterators rather than random access iterators needed by std::sort.

To resolve this issue, instead of using std::sort, employ the std::list<>::sort member function, which is designed to handle lists specifically. Here's the modified code using std::list<>::sort:

Result.poly.sort(SortDescending());

Note that the std::list<>::sort member function also requires a comparator function. The SortDescending comparator remains unchanged:

struct SortDescending
{
    bool operator()(const term& t1, const term& t2)
    { 
        return t2.pow < t1.pow; 
    }
};

By utilizing std::list<>::sort with the SortDescending comparator, you can successfully sort your list in descending order based on the 'pow' member of the 'term' structure.

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