On Fri, 2009-03-27 at 12:26 +0100, Henning Thielemann wrote:
On Thu, 26 Mar 2009, wren ng thornton wrote:
Functions like uncons and viewL are nicer (because they're safe), but they can have overhead because they're unnecessarily complete (e.g. the Maybe wrapper can be avoided if we know a-priori that Just will be the constructor used).
If you know, it's always Just, then don't use Maybe. There must be some point in your program, from where it is sure, that it is always Just and that is the point where to leave Maybe. When I searched my old code for fromJust and head and review it carefully, I could eliminate them in most cases.
In another thread (Grouping - Map/Reduce)
Yes, grouping is the one where I most often find the need for head or partial patterns. The function group produces a list of non-empty lists but that is not reflected in the type. On the other hand, actually reflecting it in the type would make it more awkward: group :: Eq a => [a] -> [(a,[a])] Duncan