C++26 Ranges: Better Infrastructure

This article discusses the improvements and infrastructure related to ranges in C++26. It provides insights into the design and implementation aspects of the new features.

From the article

C++26 ranges isn’t only about new view adaptors . Three changes landed that don’t give you new ways to compose pipelines but fix real problems: containers can now reserve space for lazy ranges that don’t know their exact size, <random> finally works with ranges, and ranges::to no longer forces you into a | pipeline when a simple function call would do.

Here’s a scenario that might have bothered you: you have a views::transform pipeline that maps Unicode codepoints to their uppercase equivalents. A single “ss” might become “SS” — you can’t know the output length in advance. When you ranges::to<std::vector>() the result, the implementation has two bad choices: traverse the range twice (once to count, once to fill), or call push_back repeatedly and eat the reallocations.

P2846R6 introduces…

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