Re: [Pharo-dev] [ANN] Grouper



Hello,

I made a small library that reify grouping (that one does via #groupBy: usually): Grouper https://github.com/juliendelplanque/Grouper

It is designed in the same spirit as SortFunction, but for grouping.

Quick example:

The following code snippet using Grouper:

(10 to: 50) groupUsing: [ :integer | integer asString first ].
"an OrderedDictionary(
  $1->#(10 11 12 13 14 15 16 17 18 19)
  $2->#(20 21 22 23 24 25 26 27 28 29)
  $3->#(30 31 32 33 34 35 36 37 38 39)
  $4->#(40 41 42 43 44 45 46 47 48 49)
  $5->#(50))"

is equivalent to the following code snippet using built-in #groupedBy: method:

(10 to: 50) groupedBy: [ :integer | integer asString first ]
"an OrderedDictionary(
  $1->#(10 11 12 13 14 15 16 17 18 19)
  $2->#(20 21 22 23 24 25 26 27 28 29)
  $3->#(30 31 32 33 34 35 36 37 38 39)
  $4->#(40 41 42 43 44 45 46 47 48 49)
  $5->#(50))"

The advantage of using it is that it allows one to compose grouper objects.

Thus, it is easy to describe grouping on 2 or 3 levels.

Fore example:

The power of Grouper is that group description are first-class objects. Thus, it is possible to compose group descriptions in order to group a flat collection on multiple levels.

For example:

groupComposition := [ :integer | integer asString first ] grouper , [ :integer | integer asString second ].
(10 to: 50) groupUsing: groupComposition.
"an OrderedDictionary(
  $1->an OrderedDictionary(
    $0->#(10) $1->#(11) $2->#(12) $3->#(13) $4->#(14) $5->#(15) $6->#(16) $7->#(17) $8->#(18) $9->#(19))
  $2->an OrderedDictionary(
    $0->#(20) $1->#(21) $2->#(22) $3->#(23) $4->#(24) $5->#(25) $6->#(26) $7->#(27) $8->#(28) $9->#(29))
  $3->an OrderedDictionary(
    $0->#(30) $1->#(31) $2->#(32) $3->#(33) $4->#(34) $5->#(35) $6->#(36) $7->#(37) $8->#(38) $9->#(39))
  $4->an OrderedDictionary(
    $0->#(40) $1->#(41) $2->#(42) $3->#(43) $4->#(44) $5->#(45) $6->#(46) $7->#(47) $8->#(48) $9->#(49))
  $5->an OrderedDictionary($0->#(50)))"

On the github, there are more example showing how to build trees with custom objects.

Any feedback for this library is welcome.

I would like to propose it to Pharo in the near future because it would simplify a lot of code in DrTests (related to result tree views, the tree on the right of the UI).

I don't know if it will be possible before next release as we are in feature freeze.

Cheers,

Julien