Understanding the Filter View to Use It Right
summary
C++20 filter_view caches the first matching iterator so initial begin can be amortized constant but later calls become cheap, which creates hidden state: modifying elements that make them fail the predicate or concurrently calling begin/empty/front yields undefined behavior. Templates can fail to accept piped filters unless you use forwarding references or wrap with std::ranges::subrange or std::views::all. C++23 adds owning view fixes; measured microbenchmarks show a manual cache (reverse+drop trick) can be much faster for repeated iterations. Use filters carefully, prefer single-pass or explicit caching.
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chapters (8)
- 0:00Filter views in C++20
- 8:59How filter views work
- 26:55Performance issues with views
- 39:50Caching in filter views
- 51:43Solutions for view limits
- 1:02:28Is caching worth it?
- 1:16:33Constness and ownership in views
- 1:23:45Safe use of filter views
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