Chunks in drasil-lang that use Maybe instead of Lenses

[Ant13731]

Here is a list of types that use Maybe (referring to the Rationalizing data structures project). Each one is formatted so that the list above encases the type, the list below contains the dependencies of the type, and the type itself is marked as a task.

Chunk types

• UncertainChunk
  • ConstrainedChunk
    • Maybe Expr, QuantityDict, [ConstraintE]
• UncertQ
  • ConstrConcept
    • Maybe Expr, DefinedQuantityDict, [ConstraintE]
• UnitalChunk, ConstrConcept
  • DefinedQuantityDict
    • Maybe UnitDefn, ConceptChunk, Stage -> Symbol, Space
• ConceptChunk, QuantityDict
  • IdeaDict
    • Maybe String, NamedChunk
• ConstrainedChunk, QDefinition, NamedArgument, UnitaryChunk
  • QuantityDict
    • Maybe UnitDefn, IdeaDict, Space, Stage -> Symbol
• UncertainChunk, UncertQ
  • Uncertainty
    • Maybe Double, Maybe Int

Classes

• --
  • MayHaveUnit
    • Maybe UnitDefn
• --
  • HasDerivation
    • lens to Maybe Derivation
• --
  • HasReasVal
    • lens to Maybe Expr

Other

• --
  • ListType, ListTuple, RawContent
    • not a chunk, but still uses Maybe String or Maybe Int

Edit: Related to #1808 and #2614

[balacij]

I believe that @Awurama-N has started work on the first 2 components (UncertainChunk + UncertQ). I'm not quite sure where the ticket went however.

[JacquesCarette]

Yes, @Awurama-N was working on that. I see that maybe there is an easier set of things to change -- the Maybe UnitDefn in DefinedQuantityDict should simply be deleted. Of course, it's not that easy! The proper process will involve seeing what the actual calls to the various dqd constructors are. But this should be doable.

So @Awurama-N can you open a new issue, where the first part will be to see all calls to dqd, dqdNoUnit, dqd', dqdWr and dqdQd in all of Drasil (not just the examples). We'll see what should be done from there. This is definitely a really awful wart that can be fixed.

[balacij]

So, I believe this ticket was about analyzing which Maybe and trying to get rid of Maybe usage. However, I'm not sure I fully understand why we're trying to get rid of Maybe.

[samm82]

I think we may have backtracked on trying to do this and will continue to use Maybe. However, the specifics of when this happens throughout the Drasil process is yet to be determined and requires more thought

[JacquesCarette]

Right, I think I may have changed my mind on Maybe. We can and should use it for truly optional information.

We should never use it if we always expect to get a Just and getting a Nothing is an error.