Comment by g9550684

9 hours ago

> convert tables to lists

array languages give you concepts for thinking about these problems where you can succinctly express that entire talk in a single sentence, something like "inverted tables improve cache locality and optimize for time and space, prefer them where it matters". yes, got it, also a well known conclusion in array world.

a table is a 2 dimensional data that stores your records row by row and the items of a column all have the same data type. the way an array of structs would. an inverted table is a list of original table's columns. like a struct of arrays.

so if you have a table,

     x
  ┌────┬──────┬─┬─────────┐
  │mob1│level1│0│0.0243902│
  ├────┼──────┼─┼─────────┤
  │mob2│level2│1│0.0147059│
  ├────┼──────┼─┼─────────┤
  │mob3│level2│0│0.0120482│
  └────┴──────┴─┴─────────┘

there's an idiom for converting it to an inverted table

     ]y=:(<@(>"1)@|:)x
  ┌────┬──────┬─────┬─────────────────────────────┐
  │mob1│level1│0 1 0│0.0243902 0.0147059 0.0120482│
  │mob2│level2│     │                             │
  │mob3│level2│     │                             │
  └────┴──────┴─────┴─────────────────────────────┘

you can then splice it across variables,

     'name level isactive v'=:y
     isactive
  0 1 0