Hi nicolas
While I know the ascending and other protocol, it is still unclear to
me the composition aspect. Did Travis write a tutorial
can we can use as documentation/comment?
BTW
"Example: #('abc' 'de' 'fghi') sorted: #size asscending"
=>
"Example: (#('abc' 'de' 'fghi') sorted: #size) ascending
=> show the result"
Stef
PS: In Pharo we do not remove history of methods for the fun.
I can tell you that I do not really like Git but I do not want our
language to be looking like a terrible system just because it does not
use a modern versioning control system.
I do not expect that we will move to another versioning control system
in the near future so we will be able to take advantage of the git
infrastructure.
And versioning code with resources and decent branch support will be
game changing.
On Mon, Nov 6, 2017 at 12:06 AM, Nicolas Cellier
<[email protected]> wrote:
> I've put some of the proposed composition features into
>
> http://source.squeak.org/inbox/Collections-nice.766.mcz
> http://source.squeak.org/inbox/CollectionsTests-nice.283.mcz
>
> http://source.squeak.org/inbox/Collections-nice.766.diff
> http://source.squeak.org/inbox/CollectionsTests-nice.283.diff
>
> SInce it's Squeak based, it uses <=>, but never mind, that's the same
> functions.
>
>
> Stephane: the original comments were from Travis Griggs.
> It's more a tutorial for using the SortFunction than a detailed explanation
> of implementation.
>
> The original idea is that oSortFunction are composable.
> For example, it's possible to chain sorting on a first criterion, then
> resort on a second criterion if objects have same rank with first.
>
> For this, we need a to distinguish when objects have same rank (=) and
> cannot use a binary result (Boolean) like legacy sortBlock,
> So we rather need a ternary comparison (<=>).
>
> This thread is about extending composition, and generalizing implementation
> by composition (like Xtreams)
> - for sorting nil first (or last)
> - for reversing the order
> - for sorting properties with any collation order, and not just default <=>
>
> 2017-11-05 17:52 GMT+01:00 Stephane Ducasse <[email protected]>:
>>
>> Hi guys
>>
>> Do you have some nice comments somewhere? because I do not understand
>> anything about this thread.
>> I check the code and the comments are well... unclear and confusing.
>>
>> Stef
>>
>> On Sun, Nov 5, 2017 at 4:15 PM, Nicolas Cellier
>> <[email protected]> wrote:
>> >
>> >
>> > 2017-11-05 16:06 GMT+01:00 Denis Kudriashov <[email protected]>:
>> >>
>> >>
>> >> 2017-11-05 11:33 GMT+01:00 Nicolas Cellier
>> >> <[email protected]>:
>> >>>
>> >>>
>> >>> Ah, I messed up, UndefinedSorter must not be chained, it must be a
>> >>> wrapper!
>> >>> Otherwise comparing to nil will resort to sorting by properties and
>> >>> fail...
>> >>>
>> >>> SortFunction>>undefinedFirst
>> >>> ^UndefinedSorter descending wrap: self
>> >>>
>> >>> UndefinedSorter>> collate: value1 with: value2
>> >>> "sort all nil according to the direction (first if -1, last if
>> >>> +1), then"
>> >>> value1 ifNil: [value2 ifNil: [^0] ifNotNil: [^direction]].
>> >>> value2 ifNil: [^direction negated].
>> >>> ^sorterForNonNil collate: value1 with: value2
>> >>>
>> >>> It's important to have the UndefinedSorter :
>> >>> - decoupled from property sort, because it can be generally
>> >>> usefull
>> >>> - collating 2 nil as 0, so that another property can be chained
>> >>
>> >>
>> >> I like your idea.
>> >> It also forced me to think that direction itself should be implemented
>> >> as
>> >> wrapper. I would name it InvertedSortFunction:
>> >>
>> >> InvertedSortFunction>>collate: value1 with: value2
>> >> ^(actualSortFunction collate: value1 with: value2) * -1
>> >>
>> >>
>> >> If we will do it then direction will be not part of SortFunction. And
>> >> all
>> >> current functions will be in fact ascending.
>> >> And to explicitly reflect this fact I would introduce
>> >> AscendingSortFunction as their superclass.
>> >> InvertedSortFunction and ChainedSortFunction will stay subclasses of
>> >> SortFunction.
>> >>
>> >> So what you think?
>> >
>> >
>> > Yes, I was thinking the same.
>> > On another hand, direction makes thing symmetric and has its elegance
>> > too.
>> > What I don't like with it is that it forces the library to have two
>> > different messages for the same thing:
>> > - collate:with: in base class accounting for direction
>> > - threeWayCompare:with: in every subclass
>> >
>> > The fact to hardcode the direction in base class could be seen as an
>> > optimization too.
>> > I'm not sure what Sista optimization could bring in this case, because
>> > the
>> > selectors may get megamorphic...
>> >
>> >
>> >>
>> >>>
>> >>>
>> >>> In
>> >>>
>> >>> people sortBy: #name ascending undefinedFirst , #age descending
>> >>>
>> >>> we could then have people with name nil still sorted by age, what is
>> >>> not
>> >>> possible with current implementation
>> >>>
>> >>
>> >
>>
>
