On 12/11/2015 02:21 PM, Johan Tibell wrote: > If we force strictness all the way down it's not really call-by-value > either, because the caller doesn't know what to evaluate (I think).
Not sure what you mean here. > In addition, making pattern matching strict in this way makes it hard to > mix and match strict and lazy data types (e.g. Maybe), because using a > lazy data type from another module will make it appear strict in your > code (hurting modularity). I don't think this is a case about modularity. A lazy Maybe value defined in a lazy module remains lazy; and you can pass it to lazy functions without forcing it. Only when you pattern match on it *in the strict module*, the evaluation happens. As I said, I prefer this semantics mainly because it's easier to explain: all variables (and underscores) bound in a strict module refer to WHNF values. Do you have a similarly simple explanation for the semantics you're suggesting? Roman
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