[Moose-dev] Re: Design Challenge: metrics missing value...

So basically you are trying to deal with missing values in collections.

People working with R or Python data analytics framework made some ways to work with specific data structures called dataframes where you can have some missing values.

For example you may have a look here: http://pandas.pydata.org/pandas-docs/stable/missing_data.html

On Wed, Dec 21, 2016 at 4:15 AM, stepharong stepharong@free.fr wrote:

Hi dear great OO designers

Here is a little challenges for your brainy souls :)

In Moose when we compute metrics it may happen than a tool (often external to pharo) does not compute a metrics and when we request it in moose we check and often we return a not so good -1.

I'm trying to brainstorm on a solution

• first may be the simplest way is to not invoke a metrics when it is not

computed. But it means that we should know it and that we should have a registration mechanism. After all this is probably the best solution.

• Second we were thinking to use exception but when we have multiple

entities missing one metrics.... I have serious doubts.

• Second I was thinking about having the following behavior

testCollect

    | uarray collected |
    uarray := UniformOrderedCollection new.
    uarray add: 10.
    uarray add: 20.
    uarray add: (MissingValue discarding).
    collected := uarray collect: [ :each | each ].
    self assert: collected size equals: 2.

testDo

    | res uarray |
    uarray := UniformOrderedCollection new.
    uarray add: 10.
    uarray add: 20.
    uarray add: (MissingValue discarding).
    uarray add: 40.
    res := 0.
    uarray do: [ :each | res := res + each ].
    self assert: res equals: 70.

testCollectDefaulting

    | uarray collected |
    uarray := UniformOrderedCollection new.
    uarray add: 10.
    uarray add: 20.
    uarray add: (MissingValue default: 33).
    collected := uarray collect: [ :each | each ].
    self assert: collected size equals: 3.
    self assert: collected third equals: 33

I basically started to implement

do: aBlock "Refer to the comment in Collection|do:." 1 to: self size do: [:index | (self at: index) toDo: aBlock on: self]

collect: aBlock "Evaluate aBlock with each of the receiver's elements as the argument. Collect the resulting values into a collection like the receiver. Answer the new collection."

    | newCollection |
    newCollection := self species new.
    self
            do: [ :each | each toCollect: aBlock on: newCollection ].
    ^ newCollection

and

DiscardingValue >> toCollect: aBlock on: aCollection "discard computation" ^ self

Object >> toCollect: aBlock on: aCollection

    ^ aCollection add: (aBlock value: self)

So I imagine that you see the design and I wanted to get your point of view.

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