> I wonder (genuinely asking, not being snarky) what it is about C/C++ that seems to make these issues more common? It's also possible my perception of "more common" has just been inflated by seeing multiple examples in a single week
It's an interesting question. There isn't a whole lot in common between the std::set and scanf issues except that they're both multi-pass algorithms (which I posted a comment about there), so I guess as far as the language is concerned, the question might reduce to "(Why) are multi-pass algorithms more common in C++?" I suppose one possible response, to the extent that this might be the case, might be that in C and C++ operations are so cheap (due to inlining and fewer indirections and such) that people don't blink twice before performing them multiple times, without thinking about the implications. Whereas in Python, everything is already so slow that you would try to factor out common operations if you were optimizing code. However, I'm not sure this is a broad pattern in general; e.g., the hashing example is just as bad in Python.
I think the bigger explanation might be more mundane as far as the language is concerned. Some of it is likely just accidental (there's no particular reason Python couldn't have made the same decision as C++ to implement == in terms of <, for example), and some of it is just a consequence of C and C++ programmers being more likely to look into performance issues, since that's probably why they chose said languages to begin with. Even the C++ example only dawned on me after years of experience optimizing things for performance, so given that Python is already incredibly slow to begin with, if I did see this in Python, chances are pretty good I would just assume it's just the interpreted nature of Python (or a poor set implementation) that's slow and not look into it further.
It's an interesting question. There isn't a whole lot in common between the std::set and scanf issues except that they're both multi-pass algorithms (which I posted a comment about there), so I guess as far as the language is concerned, the question might reduce to "(Why) are multi-pass algorithms more common in C++?" I suppose one possible response, to the extent that this might be the case, might be that in C and C++ operations are so cheap (due to inlining and fewer indirections and such) that people don't blink twice before performing them multiple times, without thinking about the implications. Whereas in Python, everything is already so slow that you would try to factor out common operations if you were optimizing code. However, I'm not sure this is a broad pattern in general; e.g., the hashing example is just as bad in Python.
I think the bigger explanation might be more mundane as far as the language is concerned. Some of it is likely just accidental (there's no particular reason Python couldn't have made the same decision as C++ to implement == in terms of <, for example), and some of it is just a consequence of C and C++ programmers being more likely to look into performance issues, since that's probably why they chose said languages to begin with. Even the C++ example only dawned on me after years of experience optimizing things for performance, so given that Python is already incredibly slow to begin with, if I did see this in Python, chances are pretty good I would just assume it's just the interpreted nature of Python (or a poor set implementation) that's slow and not look into it further.
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