Re: Data.Map.mapKeysMonotonic is a misleading name

4 Apr 2019


      ...
I doubt this function is used very often.
You could be mistaken.  Me, too.  Without statistical data, I have 0 
confidence in such estimates of brain 1. 
https://en.wikipedia.org/wiki/Thinking,_Fast_and_Slow

On 2019-04-04 14:46, Elliot Cameron wrote:
...
Well I'm proposing deprecation not removal. The deprecation could even 
live forever for all I care. It would point to the new name as well. Not 
to mention I doubt this function is used very often.
On Thu, Apr 4, 2019, 2:58 AM Andreas Abel mailto:andreas.abel@ifi.lmu.de> wrote:
I am not sure this subtlety is worth the breakage and annoyance to
    users
    coming with the name change.
    If you think about it, renaming the keys while preserving the tree
    structure cannot work if two old keys map to the same new key.
On 2019-04-03 17:13, Elliot Cameron wrote:
     > Yeah the clearest names seem to be really long ones:
     > mapKeysMonotonicDistinct, mapKeysInjectiveIncreasing,
     > mapKeysReferToDocs, etc.
     >
     > On Wed, Apr 3, 2019 at 11:11 AM David Feuer
    mailto:david.feuer@gmail.com
     > mailto:david.feuer@gmail.com>> wrote:
     >
     >     We can't use "increasing" because mathematically that usually
    means
     >     non-strictly increasing. Using "ascending" gets us in trouble
    with
     >     the other functions in the module that use the word in a
    non-strict
     >     sense.
     >
     >     On Wed, Apr 3, 2019, 10:46 AM Elliot Cameron
    mailto:eacameron@gmail.com
     >     mailto:eacameron@gmail.com>> wrote:
     >
     >         Hello!
     >
     >         In some recent analysis I ran into a subtlety that caught
    me by
     >         surprise: Data.Map.mapKeysMonotonic has a misleading name.
     >
     >         A monotonic function is not a strictly /increasing/ function,
     >         but merely non-decreasing. However,
    |mapKeysMonotonic| requires
     >         that it's mapping function be injective, which means it
    really
     >         only supports /increasing/ functions.
     >
     >         valid (mapKeysMonotonic (\x->  if  x`elem`  [1,2]then  2 
    else  x) (fromList [(1,"a"), (2,"b"), (3,"c")]))==  False
     >
     >         The docs hint at this with "This means that @f
     >         https://github.com/f@ maps distinct original keys to
    distinct
     >         resulting keys."
     >
     >         However, I'd propose that we deprecate this name and
    rename to
     >         something like |mapKeysIncreasing|or |mapKeysAsc| (to
    follow the
     >         pattern of other *Asc functions). We should also clarify
    the docs.
     >
     >
     >          From https://github.com/haskell/containers/issues/617
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