CODEWITHSUNDEEP
c++sortingiteratorstd
Code_JP
Code_JP

Reputation: 31

How does std::sort check if an iterator is std::random_access_iterator_tag?

I read that std::sort only accepts random access iterators. So, I expected to find code in the sort function that ensures only random access iterators are accepted, but I couldn't find any.

Why is it that std::sort can only take random access iterators? Did I miss something?

I'm using MSVC STL with C++17.

Upvotes: 2

Views: 111

Answers (1)

463035818_is_not_an_ai
463035818_is_not_an_ai

Reputation: 123114

That the iterator is a random access iterator is a requirement of std::sort. If the iterator passed to std::sort does not meet the requirements of the named requirement LegacyRandomAccessIterator then std::sort might work correctly or not. In any case the program is ill-formed. std::sort assumes that the iterator is a random access iterator, it does not have to explicitly check that it is one. std::sort uses operations that a RandomAccessIterator supports. If the iterator is not a RandomAccessIterator those operations might fail.

std::sort can check the requirements listed, but it does not have to. It's up to you to make sure the iterator meets them.

It's like you apply for a job where they require you to be able to jump 15m high. In the interview they will do the usual chat, but they will not check that you can jump that high. They assume you can, because they clearly stated it as requirement for the job. On day one you have to jump and you fail. End of story ;).

Upvotes: 4

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