CppCon 2018: Brian Ruth “std::basic_string: for more than just text”

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Lightning Talk
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[nivenfres]

Some of these little 4-5 minute videos have been great!

[MaceUA]

It's not about how good std::basic_string is. It's about how lacking the C++ standard library is, alas.

[gast]

The small buffer optimization is welcome for vector and other containers as well. Boost has small_vector but it would be appreciated if added to the std in some kind of form.

[neur]

This shows that (some of) the concepts behind basic_string are probably more generic and that there would be a better name for them.
But probably our thinking of what a string consists of, is too narrow.
In a literal sense a string of bits makes perfectly sense to me. But as a programmer I am used to the very strong and pretty narrow meaning :)

[Lttlemoi]

Now I want to try the same with std::stringstream

[kpanat]

capacity is at least size+1 for zerro terminator. In vector may be equal.

[TheThirdAttractor]

submit this as a full talk at some conference!

[thevinn]

Is it just me or is there a speck of dirt on the video that won't go away?

[kpanat]

random access because of contiguous memory It's not a separate advanage. It size is too big it's look disadvantage. So it's hard to find this big contiguous memory block. But access is quick.

[lorink]

+=, contiguous .data(), SSO: that's a really cool 'trick'.
I wonder how gcc can't drop the useless nee/delete. Is new considered to have side effects? I thought malloc my be dropped if deemed irrelevant?

[LemonChieff]

Oh god.
The problem is it's kind of hard to convey what we're doing when using std::basic_string<bool> it's kind of a hack. (That should be implemented differently)
But that's useful information. I never really thought about using std::basic_string for anything, not even a string to be honest.

[Betadel]

This requires specializing char_traits for the contained type right? Isn't it UB to add specializations to std types for non-user defined types like bool and uint64_t?

[MrAbrazildo]

I'm use to "upload" a text file to a std::string, which is faster and has many more features than working with a file. However, I never thought a std::basic_string could be faster/smaller (assembly) than a std::vector.
PS: by the way, is std::basic_string faster than std::string too?

[marcpanther]

Why are they laughing? I don't get the joke

[kevinwright]

This is absolutely a terrible! Look into the memory for these data structures. A vector<bool> is a bit array, which is kind of cool and useful. bit_states[0] returns a proxy class (design patterns), which is why you can't Lbind to it. If you look at the actual memory that gets set, and push_back(true) x 5 gives you a 0x1f in memory (its a bit set and kind of cool). If you have a basic_string<bool> and do push_back(true) x 5 you get 0x01 0x01 0x01 0x01 0x01 0x01 in memory because it's an array of 5, 8 bit values (which is why you can Lbind to it). Not the same thing as doing a bitset. It's a huge was of space.

[idldmit]

Yeah, if you want other devs who will read your code curse you, just go ahead use all stuff in the way it doesnt suppose to be used.