Hacker News Reader

The article doesn’t have any performance metrics. It mentions surprising performance cliffs but I couldn’t find details. It says there is a perf cost you can opt out of but doesn’t detail the cost or what you lose by opting out.

It sure seems from the article that there are a lot of negative performance implications. Which totally be a price worth paying! But I would not agree that the article explains what that price actually is.

View on HN

The biggest problem is that if you have a big """zero-cost-abstraction""" blob like iterator adaptors -- `Map<Filter<Fold<ArrayIter<MyType>>>>` -- and a single drop of Resilient Type is in there (i.e. MyType is resilient) then the whole thing gets polymorphically compiled and the compiler won't boil away any of the things that are supposed to be "zero cost".

How much you get burned by this kind of thing really depends on how you design APIs and where the hotspots are. Like if the big iterator blob is only ever for like 10 items, whatever. If the iterator blob is iterated inside the dylib where it's not resilient and can be inlined away, whatever.

Reply on news.ycombinator.com