[enriquto]

As a famous software philosopher said (I think it was Uriel): errors are wrong.

Or, to put it more clearly: there are no errors, only conditions that you dislike. It's better to not burden your programming with your emotional shortcomings, and treat all conditions that you may encounter on an equal footing.

You try to open a file; the file may or may not exist, and both cases are equally likely and you get to decide what your program does in each case. No need to attach an emotionally charged label like "error" in one of the two cases of the conditional. Or worse, as some emotional fanatics do, to bend an otherwise clean programming language by adding features (e.g., exceptions) that help support your sentimental disposition.

[asdfasgasdgasdg]

> both cases are equally likely

Both cases are not equally likely, though. Also, this article is not about the philosophical approach to naming errors versus exceptions. It's about the performance of two technical approaches to handling exceptional/unlikely circumstances.

[enriquto]

> Both cases are not equally likely, though.

Of course, if you call fopen with uniformly distributed random filenames then it is extremely unlikely than such files will exist. Thus it will fail with probability essentially 1. Yet, I don't want my programming language to force me to make an asymmetric distinction between the two cases.

By "equally likely" I don't mean "having equal probability to occur". This is very difficult to model, and it will depend mostly on the usage patterns of the users of the program. I mean that both cases are worth of the same attention and merit an equivalently serious treatment. No need to disparage one of the two cases as an "error" or an "exception" and require a special language construct.

[asdfasgasdgasdg]

I assure you, the file-does-not-exist case cares nothing for whether you "disparage" it by calling it an error. As for having a special language construct, the performance benefits discussed in this article are one example of why you might want to have one. If you already have it, using it to represent file not found excursions seems reasonable.