Re: Data.HashMap: Strict or lazy by default?

On Thu, Feb 17, 2011 at 4:51 PM, Johan Tibell wrote:

My current thinking is to provide lazy and strict versions in different modules. The two modules could still share the same data type. The question is, what should be the default? Haskell is a lazy language but the most common use cases for maps are strict (e.g. a map from strings to integer counters).

What about class instances? With a shared data type we can only provide one set of instances, probably the lazy ones. Assuming we used to separate data types, can we even define instances for all common classes (e.g. Functor, Foldable, Monoid) or will the strict versions violate some of the laws for these classes? Johan