On Tuesday, 25 March 2014 at 17:22:45 UTC, monarch_dodra wrote:
I think this is wrong. popping an empty range is an *Error*, and should be validated by the programmer. Because of this, it is currently not possible to use "reduce(range)" in nothrow context.
Popping an empty range is indeed an error, but that's not the issue here. The issue is whether or not it should check for empty, i.e. whether an empty input is valid. Other looping eager algorithms - like `sum` and indeed `copy` - do accept empty inputs.
I understand the issue of nothrow of course; I think it's likely that in most real-world use cases, reduce/fold will be used on guaranteed non-empty inputs, *but not always*, and I'd hate for release-build-only dangerous bugs to sneak into programs because of it.
Maybe we should have some kind of NonEmpty higher-order range type that algorithms can overload on, ala how std.container deals with Take? It could be initialized with `assumeNonEmpty(r)` and/or `checkNonEmpty(r)`.
