On Sunday, 8 August 2021 at 18:36:02 UTC, vit wrote:
Hello, is there reason why elements of input range must be copyable?
By design, not that I can think of. But it is assumed all over the place, unfortunately. You can make your `front` method return by `ref`, but you're still going to get bitten as soon as you do any `std.algorithm`-based operation, as storage classes are not inferred (https://issues.dlang.org/show_bug.cgi?id=9423) and things get passed by value to your delegates by default. The problem can also show up when you `foreach` over a range (https://issues.dlang.org/show_bug.cgi?id=15413). And finally, `std.algorithm` need to support it.
So currently you'll have to jump through a lot of hops to get it to work. It'll be much easier to use your own `map` & co to get the job done for the time being. Hopefully at some point in the near future that won't be needed anymore.
