Andrey_Karpov writes: Perhaps, readers remember my article titled "Last line effect". It describes a pattern I've once noticed: in most cases programmers make an error in the last line of similar text blocks. Now I want to tell you about a new interesting observation. It turns out that programmers tend to make mistakes in functions comparing two objects. This statement looks implausible; however, I'll show you a great number of examples of errors that may be shocking to a reader. So, here is a new research, it will be quite amusing and scary.