CODEWITHSUNDEEP
c++sorting
elexhobby
elexhobby

Reputation: 2668

Sorting array of class objects using member function

I'm not sure what is wrong with the following code, where I'm trying to sort an array of class objects using a member function comparator.

class Query {
    public:
        int start;
        int end;
        int index;
        bool operator<(const Query &b) {
            return this->start < b.start;
        }
};

Query query[q];

for (int i=0;i<q;++i) {
    cin>>query[i].start>>query[i].end;
    query[i].index = i;
}
sort(query,query+q);

I get the following error:

error: no matching function for call to ‘sort(main()::Query [(((unsigned int)(((int)q) + -0x00000000000000001)) + 1)], main()::Query*)’

Update: I figured out the cause of the error. I had included the class within my main. The problem was resolved when I moved the class definition outside main. I don't have a good enough understanding of C++/OOP to understand why this happens. I'd appreciate if somebody could explain or direct me to helpful resources.

Upvotes: 1

Views: 1642

Answers (1)

Oswald
Oswald

Reputation: 31685

Local types (i.e. types that are defined inside a function) cannot be used as template arguments in C++03 (one of the template arguments of std::sort() is the type of the objects that should be sorted). I do not know why C++03 has this restriction. C++11 does not have this restriction anymore.

Upvotes: 2

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