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 _______________________________________________ Libraries mailing list Libraries@haskell.org mailto:Libraries@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries

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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 >         _______________________________________________ >         Libraries mailing list > Libraries@haskell.org mailto:Libraries@haskell.org mailto:Libraries@haskell.org> > http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries > > > _______________________________________________ > Libraries mailing list > Libraries@haskell.org mailto:Libraries@haskell.org > http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries > _______________________________________________ Libraries mailing list Libraries@haskell.org mailto:Libraries@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries

Thanks Artyom. That's useful. In fact in highlights the original motivation for my request. Data.Map his numerous wrappers and clones (I happened to be working on monoidal-containers) and this name keeps getting spread throughout them. In the case of a monoidal-containers, mapKeysMonotonic only makes sense with a Semigroup constraint on the values (because a monotonic function can still cause keys to get merged). But now the name is even more confusing: what happens to duplicate keys: are they merged with Data.Map's infamous left-bias? Are they <>ed together? But that can't be since there is no Semigroup constraint... Your search shows that this same name is also used in IntervalMap and Agda for the very reason that it matches the name in Data.Map! So my true hope is that a) people won't be confused by this function and b) people will stop using this name in wrappers/clones if it's not *actually* the appropriate name. On Thu, Apr 4, 2019 at 9:51 AM Artyom Kazak wrote:

It's not used _very_ often, but it does appear a few times on Hackage. For instance, it's used several times in Agda source: https://codesearch.aelve.com/haskell/search?query=.mapKeysMonotonic&filter=Data.Map(+|$)&insensitive=off&space=off&precise=off&sources=on&page=1 https://codesearch.aelve.com/haskell/search?query=.mapKeysMonotonic&filter=Data.Map(+%7C$)&insensitive=off&space=off&precise=off&sources=on&page=1

On Apr 4 2019, at 3:19 pm, Andreas Abel wrote:

...

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 _______________________________________________ Libraries mailing list Libraries@haskell.org mailto:Libraries@haskell.org

mailto:Libraries@haskell.org>

http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries

_______________________________________________ Libraries mailing list Libraries@haskell.org mailto:Libraries@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries

_______________________________________________ Libraries mailing list Libraries@haskell.org mailto:Libraries@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries

_______________________________________________ Libraries mailing list Libraries@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries

I guess I just want names to say what they mean and not require me to deduce what they must mean based on other, possibly invisible, constraints. If we can come up with a good name for this then I'd even be happier if we simply added an alias with a less-confusing name and didn't even formally deprecate the other one. Can some suggest such a name? I've tossed a few out: mapKeysInjectiveIncreasing, mapKeysStrictlyIncreasing, mapKeysMonotonicDistinct On Thu, Apr 4, 2019 at 3:57 PM Andreas Abel wrote:

Elliot,

Maybe as a German I do not stumble over that use of "monotonic" in the same way as you might. In German, we have

<= monoton steigend

...

= monoton fallend < streng monoton steigend streng monoton fallend

Thus, "monoton" by itself is not a precise notion, but refers to the family of these concepts (although it is a bit sloppily often used for "monoton steigend"). The German precise name of mapKeysMonotonic would be

transformiereSchlüsselStrengMonotonSteigend

and you can see that using fully precise names get you nowhere in my context. :D

However, my question still stands what else than "strictly increasing" could be meant in "mapKeysMonotonic"? If it is not an injective function you pass to it, then what can be the advantage over the general "mapKeysWith"? And how likely is the case that a "mapKeysNonStrictlyIncreasing" would be preferable over "mapKeysWith", justifying the extra implementation of a "mapKeysNonStrictlyIncreasing"?

Cheers, Andreas

On 2019-04-04 16:58, Elliot Cameron wrote:

...

Thanks Artyom. That's useful. In fact in highlights the original motivation for my request. Data.Map his numerous wrappers and clones (I happened to be working on monoidal-containers) and this name keeps getting spread throughout them. In the case of a monoidal-containers, mapKeysMonotonic only makes sense with a Semigroup constraint on the values (because a monotonic function can still cause keys to get merged). But now the name is even more confusing: what happens to duplicate keys: are they merged with Data.Map's infamous left-bias? Are they <>ed together? But that can't be since there is no Semigroup constraint... Your search shows that this same name is also used in IntervalMap and Agda for the very reason that it matches the name in Data.Map!

So my true hope is that a) people won't be confused by this function and b) people will stop using this name in wrappers/clones if it's not /actually/ the appropriate name.

On Thu, Apr 4, 2019 at 9:51 AM Artyom Kazak mailto:yom@artyom.me> wrote:

It's not used _very_ often, but it does appear a few times on Hackage. For instance, it's used several times in Agda source:

https://codesearch.aelve.com/haskell/search?query=.mapKeysMonotonic&filter=Data.Map(+|$)&insensitive=off&space=off&precise=off&sources=on&page=1 https://codesearch.aelve.com/haskell/search?query=.mapKeysMonotonic&filter=Data.Map(+%7C$)&insensitive=off&space=off&precise=off&sources=on&page=1

...

<

https://codesearch.aelve.com/haskell/search?query=.mapKeysMonotonic&filter=Data.Map(+%7C$)&insensitive=off&space=off&precise=off&sources=on&page=1

...

On Apr 4 2019, at 3:19 pm, Andreas Abel mailto:andreas.abel@ifi.lmu.de> wrote:

> 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 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 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>

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 _______________________________________________ Libraries mailing list Libraries@haskell.org mailto:Libraries@haskell.org mailto:Libraries@haskell.org>

mailto:Libraries@haskell.org

...

...

http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries

...

_______________________________________________ Libraries mailing list Libraries@haskell.org mailto:Libraries@haskell.org mailto:Libraries@haskell.org>

http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries

...

_______________________________________________ Libraries mailing list Libraries@haskell.org mailto:Libraries@haskell.org

...

http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries

_______________________________________________ Libraries mailing list Libraries@haskell.org mailto:Libraries@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries