Question

Can someone explain in English what is going on here?

std::vector<Cat*> cats; //I get that cats is a vector of Cat objects

if (std::find(cats.begin(), cats.end(), morris) == cats.end()) {
   cats.push_back(morris);
}

Answer 1

@mlimber has already given one explanation.

I’d explain it a bit differently. In plain English, it’s a way of taking something really simple:

 std::set<Cat> cats;

 cats.insert(morris);

and making it slower (linear instead of logarithmic) and considerably harder to read or understand.

Edit: In fairness, I suppose I should add that there are a few reasons you might want to do something like this. For example, if you really need to know the order in which Cats were added to the collection, preserving the original order might make some sense. Likewise, if you’re usually using the collection in a way that benefits from them being contiguous in memory, and only rarely adding a new item, it might make more sense to store the data in a vector than an set.

A set, however, is designed to do exactly what’s being done here, so a set is the obvious choice (absent compelling reasons to use a vector that just aren’t visible in what you’ve shown).