RFE: string extension - split, strip, join

[Xecutor]

Hello.

I have some preliminary implementation split range, strip transform and join sink. But I'm not sure if they should be part of main lib or should be placed in a separate file as an optional extension.

strip takes two const iterators of input, two const iterators of separator and produces basic_string_view as output.
strip takes range of const CharT*, basic_string_view or basic_string as input and produces basic_string_view as output.
join takes range of const CharT*, basic_string_view or basic_string and const CharT*, basic_string_view or basic_string as input and produces basic_string as output.

Need to discuss this and I'll make corresponding PR.

[simonask]

It seems like join is already present as chain?

I would suggest expressing split (or split_by?) as taking an input range instead of iterator pairs. Since strings can be implicitly converted to ranges, this would work:

auto strings = "a,b"sv | split_by(",") | to_vector(); // {"a"sv, "b"sv}

[Xecutor]

I wasn't clear enough: join with separator, like inverse split : vector{{"aa","bb","cc"}} | join(":") yields std::string aa:bb:cc.

Arbitrary input range for split_by seems somewhat problematic. std::search takes two iterators of the same type as input.

[Hazurl]

To be consistent with the rest of the library, join should return a range outputting an element every other index, a sink can then be used to create a string from it. Same for split, it should take a range and return a range of range like in_groups_of.

strip, on the other hand, seems hard to implement (given its definition in the python std lib). The end trim is not possible without a lookahead, which means an allocation to store the elements.

[Xecutor]

If split_by should produce range of string_views, then these string_views should be constructed from pointer and size. I tried to do this with range as an input to split_by, but it looks quite cumbersome, and range based iterators being strictly forward iterators kind of incompatible with ability to takes distance between iterators and the memory not necessary will be continuous. The original idea was that split(" hello , world , foo , bar", ",') | string() | to_vector(); will produce vector of string_views to original string. Probably I'm missing something...