On 9 July 2016 at 03:49, David Feuer
We currently have a function mapMonotonic in Data.Set and one called mapKeysMonotonic in Data.Map. These names are confusing for two reasons:
1. In some mathematical contexts, a function is considered monotonic if it's *either* increasing or decreasing.
2. Even where monotonic specifically means *increasing*, it generally does *not* specifically mean *strictly increasing*.
The functions in question work when, and only when, the given function is strictly increasing on the elements/keys in the set/map.
I'd like to DEPRECATE these functions, and add new ones:
Data.Set: mapStrictlyIncreasing and mapStrictlyDecreasing Data.Map: mapKeysStrictlyIncreasing and mapKeysStrictlyDecreasing
With the latter function also flipping the underlying tree structure?
Data.Map presents another possibility, however. We could make the replacements more general, giving them types
Ord k => (k -> v -> (k', v')) -> Map k v -> Map k' v'
and allowing the user to map over both keys and values in one pass.
Though IIUC this provides no way of specifying that "I'm sure this function has a 1-1 monotonic relationship so you can just update the keys without changing the structure" (in the sense of there's no way to distinguish between the increasing and decreasing sense). Overall, I'm about +0.5 from the naming sense of the current functions, but have used these in the past. -- Ivan Lazar Miljenovic Ivan.Miljenovic@gmail.com http://IvanMiljenovic.wordpress.com