Bikeshed opportunity: compose vs composeWith

[Kevin Bourrillion]

As soon as I hit send I realized I was thinking of the *by() methods as
taking Comparators as their parameters, which is wrong.  Perhaps responding
on this thread at 2:45 am was a suboptimal idea. Sorry!


On Thu, Nov 29, 2012 at 2:43 AM, Kevin Bourrillion <kevinb at google.com>wrote:

> Note that a very natural way that users are naming their comparator
> instances is to start with "by" :  Comparator<User> byIdDesc, or
> Comparator<Account> BY_BALANCE, etc. I know that this is "common" in Google
> code (I could get more specific if necessary).
>
> These, of course, would become dreadful names overnight if the method
> names we use themselves end in "by".
>
> That's just one more small reason why my preference is still for
> comparing/thenComparing.
>
>
>
> On Tue, Nov 27, 2012 at 5:11 PM, Raab, Donald <Donald.Raab at gs.com> wrote:
>
>> Here's my last try at "by".  It's concise and readable in my opinion.
>>  For any of us collections framework developers who already have sortBy,
>> minBy and maxBy on our protocols it also offers nice symmetry when used in
>> the fluent form with static imports.
>>
>> people.sort(by(Person::getLast).thenBy(Person::getFirst))
>> people.min(by(Person::getLast).thenBy(Person::getFirst))
>> people.max(by(Person::getLast).thenBy(Person::getFirst))
>>
>> Comparator<Person> byLastThenByFirst =
>> Comparators.by(Person::getLast).thenBy(Person::getFirst)
>>
>> or
>>
>> Comparator<Person> byLastThenByFirst =
>> by(Person::getLast).thenBy(Person::getFirst)
>>
>> Vs.
>>
>> people.sort(comparing(Person::getLast).thenComparing(Person::getFirst))
>> people.min(comparing(Person::getLast).thenComparing(Person::getFirst))
>> people.max(comparing(Person::getLast).thenComparing(Person::getFirst))
>>
>> Comparator<Person> comparingLastThenComparingFirst =
>> Comparators.comparing(Person::getLast).thenComparing(Person::getFirst)
>>
>> or
>>
>> Comparator<Person> comparingLastThenComparingFirst =
>> comparing(Person::getLast).thenComparing (Person::getFirst)
>>
>>
>> Both read ok, so whatever the consensus is.
>>
>> > -----Original Message-----
>> > From: Brian Goetz [mailto:brian.goetz at oracle.com]
>> > Sent: Tuesday, November 27, 2012 11:04 AM
>> > To: Kevin Bourrillion
>> > Cc: Raab, Donald [Tech]; Sam Pullara; lambda-libs-spec-
>> > experts at openjdk.java.net
>> > Subject: Re: Bikeshed opportunity: compose vs composeWith
>> >
>> > I like "thenComparing".  Done?
>> >
>> > Separately, would "reverseOrder" be better / more consistent for the
>> > extension method on Comparator than the current "reverse"?  (There's
>> > already a Collections.reverseOrder static method.)
>> >
>> > On 11/27/2012 10:35 AM, Kevin Bourrillion wrote:
>> > > I think it's very helpful for these two names to have parallel
>> > structure:
>> > >
>> > > comparingBy / thenBy
>> > >
>> > > or
>> > >
>> > > comparing / thenComparing
>> > >
>> > >
>> > >
>> > >
>> > > On Mon, Nov 26, 2012 at 2:48 PM, Raab, Donald <Donald.Raab at gs.com
>> > > <mailto:Donald.Raab at gs.com>> wrote:
>> > >
>> > >     What about this?
>> > >
>> > >     people.sort(comparing(Person::getLast).thenBy(Person::getFirst))
>> > >
>> > >      > -----Original Message-----
>> > >      > From: Raab, Donald [Tech]
>> > >      > Sent: Monday, November 26, 2012 5:45 PM
>> > >      > To: 'Brian Goetz'; Sam Pullara
>> > >      > Cc: lambda-libs-spec-experts at openjdk.java.net
>> > >     <mailto:lambda-libs-spec-experts at openjdk.java.net>
>> > >      > Subject: RE: Bikeshed opportunity: compose vs composeWith
>> > >      >
>> > >      > Just out of curiosity,I opened up Microsoft Excel and looked
>> > how they
>> > >      > word multi-level sorts.
>> > >      >
>> > >      > Sort By -> Column A
>> > >      > Then By -> Column B
>> > >      > Then By -> Column C
>> > >      > Etc.
>> > >      >
>> > >      > So "then" in the wording definitely looks good.  Not sure if
>> > there is
>> > >      > anything better than thenCompare.
>> > >      >
>> > >      > This would be cool to read, but is a different animal.
>> > >      >
>> > >      > people.sortBy(Person::getLast).thenBy(Person::getFirst)
>> > >      >
>> > >      > We use the word "chain" on our Comparators static utility
>> > class in GS
>> > >      > Collections with varargs.  But since you are adding this
>> > method to
>> > >      > Comparator, not sure if chain or chainWith would be a good
>> > name.
>> > >      >
>> > >      > > -----Original Message-----
>> > >      > > From: lambda-libs-spec-experts-bounces at openjdk.java.net
>> > >     <mailto:lambda-libs-spec-experts-bounces at openjdk.java.net>
>> > >      > > [mailto:lambda- <mailto:lambda->
>> > >     libs-spec-experts-bounces at openjdk.java.net
>> > >     <mailto:libs-spec-experts-bounces at openjdk.java.net>] On Behalf
>> > >      > > Of Brian Goetz
>> > >      > > Sent: Monday, November 26, 2012 3:07 PM
>> > >      > > To: Sam Pullara
>> > >      > > Cc: lambda-libs-spec-experts at openjdk.java.net
>> > >     <mailto:lambda-libs-spec-experts at openjdk.java.net>
>> > >      > > Subject: Re: Bikeshed opportunity: compose vs composeWith
>> > >      > >
>> > >      > > I like the "then" convention to indicate sequencing.  In
>> > context:
>> > >      > >
>> > >      > > people.sort(comparing(Person::getLast)
>> > >      > >                .thenCompare(comparing(Person::getFirst)))
>> > >      > >
>> > >      > >
>> > >      > >
>> > >      > > On 11/26/2012 3:04 PM, Sam Pullara wrote:
>> > >      > > > How about something that sounds more comparator specific:
>> > >      > > >
>> > >      > > > comparator1.thenCompare(comparator2)
>> > >      > > >
>> > >      > > > Sam
>> > >      > > >
>> > >      > > > On Nov 26, 2012, at 11:57 AM, Kevin Bourrillion
>> > >     <kevinb at google.com <mailto:kevinb at google.com>
>> > >      > > > <mailto:kevinb at google.com <mailto:kevinb at google.com>>>
>> > wrote:
>> > >      > > >
>> > >      > > >> So... comparator1.compound(comparator2)?
>> > >      > > >>
>> > >      > > >>
>> > >      > > >> On Mon, Nov 26, 2012 at 11:10 AM, Brian Goetz
>> > >      > > <brian.goetz at oracle.com <mailto:brian.goetz at oracle.com>
>> > >      > > >> <mailto:brian.goetz at oracle.com
>> > >     <mailto:brian.goetz at oracle.com>>> wrote:
>> > >      > > >>
>> > >      > > >>         However, this is the first time I'm noticing that
>> > you're
>> > >      > > using
>> > >      > > >>         the name
>> > >      > > >>         compose() not only for function composition, but
>> > >     also for
>> > >      > > >>         forming a
>> > >      > > >>         compound comparator.  Has it been suggested that
>> > we not
>> > >      > > reuse the
>> > >      > > >>         compose() name to mean this other thing?  Note
>> > that
>> > >     there
>> > >      > > does
>> > >      > > >>         exist a
>> > >      > > >>         compose operation for Comparators, but it's
>> > (Function,
>> > >      > > >>         Comparator) ->
>> > >      > > >>         Comparator (Guava puts it in the other order and
>> > >     calls it
>> > >      > > >>         "onResultOf",
>> > >      > > >>         which I'm not recommending).
>> > >      > > >>
>> > >      > > >>
>> > >      > > >>     It has not been suggested until now.  I am fine
>> > calling this
>> > >      > > >>     something that does not contain the string "compose".
>> > >       The key
>> > >      > > >>     concept is "I have two comparators, and I want to
>> > build a
>> > >      > > >>     dictionary-order comparator for (O1, O2)."
>> > >      > > >>
>> > >      > > >>     I am fine with .compose() for functions.
>> > >      > > >>
>> > >      > > >>     I think .compose(other) is too cryptic for
>> > comparators.  I
>> > >      > think
>> > >      > > >>     .composeWith() is better; I can imagine there are
>> > other
>> > >     things
>> > >      > > >>     that are also better.  Now taking suggestions.
>> > (Though
>> > >      > > onResultOf
>> > >      > > >>     does not seem better.)
>> > >      > > >>
>> > >      > > >>
>> > >      > > >>
>> > >      > > >>
>> > >      > > >> --
>> > >      > > >> Kevin Bourrillion | Java Librarian | Google, Inc.
>> > >      > > >> |kevinb at google.com <mailto:kevinb at google.com>
>> > >     <mailto:kevinb at google.com <mailto:kevinb at google.com>>
>> > >      > > >>
>> > >      > > >
>> > >
>> > >
>> > >
>> > >
>> > > --
>> > > Kevin Bourrillion | Java Librarian | Google, Inc. |kevinb at google.com
>> > > <mailto:kevinb at google.com>
>> > >
>>
>
>
>
> --
> Kevin Bourrillion | Java Librarian | Google, Inc. | kevinb at google.com
>
>


-- 
Kevin Bourrillion | Java Librarian | Google, Inc. | kevinb at google.com