使用 std::ranges::to 将 std::ranges::lazy_split_view 收集到 std::vector

Question

在 Rust 中，我可以写（Rust Playground）：

let vec = "Hello-+-Rust-+-!".split("-+-").collect::<Vec<_>>();
println!("{:?}", vec); // ["Hello", "Rust", "!"]

我想在 C++23 中做同样的事情。

我写了（编译器资源管理器）：

#include <ranges>
#include <vector>
#include <print>

int main()
{
    auto vec = "Hello-+-C++-+-23-+-!" 
        | std::ranges::views::lazy_split(std::string_view("-+-"))
        | std::ranges::to<std::vector<std::string_view>>();

    std::println("{}", vec);
}

但是 clang 报了 2 个错误：

In file included from <source>:1:
In file included from /opt/compiler-explorer/clang-trunk-20240518/bin/../include/c++/v1/ranges:416:
/opt/compiler-explorer/clang-trunk-20240518/bin/../include/c++/v1/__ranges/to.h:134:18: error: no matching function for call to 'to'
  134 |           return ranges::to<range_value_t<_Container>>(std::forward<decltype(__elem)>(__elem));
      |                  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
...
/opt/compiler-explorer/clang-trunk-20240518/bin/../include/c++/v1/__ranges/to.h:133:27: error: invalid operands to binary expression ('ref_view<lazy_split_view<ref_view<const char[21]>, string_view>>' (aka 'ref_view<std::ranges::lazy_split_view<std::ranges::ref_view<const char[21]>, std::string_view>>') and '__range_adaptor_closure_t<__bind_back_t<__fn, tuple<(lambda at /opt/compiler-explorer/clang-trunk-20240518/bin/../include/c++/v1/__ranges/to.h:133:46)>>>' (aka 'std::ranges::__range_adaptor_closure_t<std::__bind_back_t<std::ranges::views::__transform::__fn, std::tuple<(lambda at /opt/compiler-explorer/clang-trunk-20240518/bin/../include/c++/v1/__ranges/to.h:133:46)>>>'))
  133 |         ref_view(__range) | views::transform([](auto&& __elem) {
      |         ~~~~~~~~~~~~~~~~~ ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  134 |           return ranges::to<range_value_t<_Container>>(std::forward<decltype(__elem)>(__elem));
      |           ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  135 |         }),
      |         ~~
...
2 errors generated.
ASM generation compiler returned: 1

我怎么知道哪里出了问题？

Answer 1

views::lazy_split

是lazy，这意味着分割子范围最多只能满足

forward_range

，你应该使用

views::split

auto vec = "Hello-+-C++-+-23-+-!" 
    | std::ranges::views::split(std::string_view("-+-"))
    | std::views::transform([](auto r) { return std::string_view{r}; })
    | std::ranges::to<std::vector>();

std::println("{}", vec);

演示