The motivation for this extension, which is detectable by a conforming program, and thus non-conforming, is to make vector<bool> behave more like vector<char> with respect to references (const and otherwise). Introduction Since 1998, vector<bool> has been derided as “not quite a container.” LWG 96, one of the very first LWG issues, launched the debate. Today, … Read more
Is it guaranteed that all compliant compilers have the same experimental features? No, experimental features are optional. Are experimental features prone to big changes that make them unreliable? Yes, the C++ committee might even decide to abandon a feature or in the process of standardization a defect might come up that would force a feature … Read more
<filesystem> (added in C++17) makes this very straightforward. #include <cstdint> #include <filesystem> // … std::uintmax_t size = std::filesystem::file_size(“c:\\foo\\bar.txt”); As noted in comments, if you’re planning to use this function to decide how many bytes to read from the file, keep in mind that… …unless the file is exclusively opened by you, its size can be … Read more
If you need to iterate over a queue then you need something more than a queue. The point of the standard container adapters is to provide a minimal interface. If you need to do iteration as well, why not just use a deque (or list) instead?
The standard library favours elementary algorithms. Containers and algorithms should be independent of each other if possible. Likewise, algorithms that can be composed of existing algorithms are only rarely included, as shorthand. If you require a transform if, you can trivially write it. If you want it /today/, composing of ready-mades and not incur overhead, … Read more
The libc++ basic_string is designed to have a sizeof 3 words on all architectures, where sizeof(word) == sizeof(void*). You have correctly dissected the long/short flag, and the size field in the short form. what value would __min_cap, the capacity of short strings, take for different architectures? In the short form, there are 3 words to … Read more
It means not found. It is usually defined like so: static const size_t npos = -1; It is better to compare to npos instead of -1 because the code is more legible.
Here’s a sequence pseudo-container I pieced together from ยง 23.2.1\4 Note that the iterator_category should be one of std::input_iterator_tag, std::output_iterator_tag,std::forward_iterator_tag,std::bidirectional_iterator_tag,std::random_access_iterator_tag. Also note that the below is technically more strict than required, but this is the idea. Note that the vast majority of the “standard” functions are technically optional, due to the awesomeness that is iterators. … Read more
valarray is kind of an orphan that was born in the wrong place at the wrong time. It’s an attempt at optimization, fairly specifically for the machines that were used for heavy-duty math when it was written — specifically, vector processors like the Crays. For a vector processor, what you generally wanted to do was … Read more
This is implementation dependent: Standard 23.1.2.8: The insert members shall not affect the validity of iterators and references to the container, and the erase members shall invalidate only iterators and references to the erased elements. Maybe you could try this — this is standard conforming: for (auto it = numbers.begin(); it != numbers.end(); ) { … Read more