C++ operator overloading, understanding the Google style guide

c++, syntax

Solution

A functor type would be more like this:

struct CatalogueItemLessThan
{
    bool operator()(const CatalogueItem &a, const CatalogueItem &b)
    {
    }    
};

Then the usage would look like this:

list<CatalogueItem> my_list;

// this is just me playing around
CatalogueItem items[2];
items[0] = CatalogueItem(4, string("box"), string("it's a box"));
items[1] = CatalogueItem(3, string("cat"), string("it's a cat"));

my_list.push_back(items[0]);
my_list.push_back(items[1]);

my_list.sort(CatalogueItemLessThan());

The main advantage of this, is that is allows you to decouple sorting from the object itself. You can now provide as many types of sorting as you want, and use them in different places. (For example, string can be sorted in lexical order, or case-insensitively, or "naturally".

The advantage of using a functor as opposed to a loose function is that you can pass parameters into the comparison to modify how the functor should behave.

In general, the Google style-guide is not really the best style guide out there (IMHO especially their taking exception to exceptions, but that's another discussion). If an object has an obvious sorting order, I often add in a default `operator<`. If later, there are extra sort orders I want to add, then I add in loose functions. If at a later time, I need to add parameters to the sort order, then I make them into functors. There's no sense in adding in complexity before it's needed.

Problem

Original source

Related problems

• Natural Sorting algorithm