Assign incremental IDs to sets of functions

[tlalearner]

I have a very simple initialization for a function as follows:

sampleTableINIT ==

        sampleTable = [person \in group |-> 

            [

                status |-> "Active",

                divisions |-> {[assignedDivision |-> division] : division \in getDivisions(person)} 

            ]]

Here is a sample result from the definition:

[Sam :> [status |-> "Active", divisions |-> { [assignedDivision |-> "Sales"]]  

[Mary :> [status |-> "Active", divisions |-> { [assignedDivision |-> "Sales"], [assignedDivision |-> "CS" }]

What I'd like to accomplish is simple: Per person entry, I'd like to assign an ID per division. The result below is what I want:

[Sam :> [status |-> "Active", divisions |-> { [id |-> 1, assignedDivision |-> "Sales"]]    

[Mary :> [status |-> "Active", divisions |-> { [id |-> 1, assignedDivision |-> "Sales"], [id |-> 2, assignedDivision |-> "CS" }]  

Order on ID assignment does not matter. Is there an easy way to do this rather than mutating the function in a future state?

[Stephan Merz]

Fundamentally, you are trying to convert a set to a sequence that contains each element of the set exactly once. The module SequenceExt from the Community Modules contains an operator that does that:

IsInjective(s) == \A i, j \in DOMAIN s: (s[i] = s[j]) => (i = j)
SetToSeq(S) == CHOOSE f \in [1..Cardinality(S) -> S] : IsInjective(f)

Now you can define your operator as follows:

tableInit ==

  [person \in group |->

      [ status |-> "Active",

        divisions |-> LET divs == SetToSeq(getDivisions(person))

                      IN  { [id |-> i, assignedDivision |-> divs[i]] :

                            i \in 1 .. Len(divs) } ]]

Instead of representing `divs' as a set of records with id fields, you could represent it as a sequence where the id is implicit in the position of the element in the sequence. However, I wonder if you are at the right level of abstraction for your specification: all the information that you need is contained in the set `group' and the operator `getDivisions'. Is it important to construct an explicit data structure that materializes that information, in particular since you don't care about the order of IDs?

Stephan

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