Functional

[mohamed-barakat]

No description provided.

[mohamed-barakat]

Result of discussion with Fabian:

The compiler currently supports these two (information preserving) rules:

1. func( L[index] ) => List( L, func )[index]
2. List( list_of_lists[index], func ) => List( list_of_lists, list -> List( list, func ) )[index]

Fabian experience:

If one reverts these two rules one loses hoisting and the performance drops. This was observed with

• PushoutComplement in SkeletalFinSets
• The Hom-structure in a presheaf category (where in the example the number of morphisms was 39).
• Somewhere in the MatrixCategory
• ...

It seems that these rules are universally reasonable for categories where "matrices" (sources and targets are small ints) are involved (abelian world) but are not universally reasonable for categories where "functions" (sources or targets could be big ints) are involved (topos world).

[zickgraf]

Additional notes:

• The post-processing reverses the rule

  func( L[index] ) => List( L, func )[index]
  

  in special cases. Possibly, a sweet spot between the "list" and the "functional" approach could be reached by enhancing the list of cases where the reversed rule is applied in the post-processing step.
• Conversely, if the solution actually is to always use the reverse rule in the topos world, this post-processing step can probably simply be removed.