Re: Data.Map.mapKeysMonotonic is a misleading name

4 Apr 2019


      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  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> 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> 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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