Avoid filter view in general use cases

[LearnWebGitHub]

For most scenarios, caching begin() is highly misleading.

cplusplus/papers#2147

[jwakely]

"Avoid filter view" is not a good guideline. "Don't do dumb things with views" would make a great guideline. Don't re-use a view after you've modified the underlying storage in a way that invalidates the view. And caching is not the cause of many of the paper's complaints about filter view.

Anyway, the proposal you linked to was superseded by another paper which addressed many of the concerns: combine views::filter with views::as_input if you don't need multi-pass and/or need const iteration. But it's still the case that views have reference semantics not value semantics, so don't assume you can treat them like containers. They're not containers. Different things are different.