Comment by dataflow

Counter-point: while in many situations this isn't the right approach, it's worth recognizing when this is the right approach, because they can look awfully similar. An example of this is graph searching, e.g. BFS or Dijkstra's algorithm. The typical implementation is a function. But if you make Dijkstra a class, with (say) a function to iterate through nodes, it lets you do several things that would be difficult with a function: (a) you can now re-use the same object for computing distances to multiple vertices, which allows incremental search, (b) you can now fork/copy the object and continue searching on different extensions of the original graph, (c) you can now save & restore the searcher state to pause the search & continue it later, (d) you can do multiple searches across one or more graphs in lockstep. IMHO these are very much not obvious, and to someone who doesn't recognize what's going on, a class for something like BFS will look exactly like an "OO antipattern", when in reality it's actually providing significant additional functionality for more complicated situations.