Summary data display

[apjanke]

Gonna need to do a whole type hierarchy for this.

• Each variable needs a custom sub-display output based on its type.
• Since per-variable summary types vary, we'll need a heterogeneous collection of custom per-variable summary objects.
• Maybe we could collect those in a struct of sub-objects.
  • But we'll also need object-level summary data for object-level stuff like tbl.Description.
  • So, a table-level object that has a collection of table-level properties, and then a struct of heterogeneous per-variable summary objects?

I'm thinking:

• octave.table.internal.TableSummary
  • field .TableProperties: struct of (name, string)
  • field .VariableSummaries: struct of (name, octave.table.internal.VariableSummary subclasses)
• octave.table.internal.VariableSummary
  • abstract type with concrete subtypes for various variable types
  • method print(this, indent) for incorporation into indented table summary output
  • concrete subclasses for:
    • Numeric (with polymorphic handling of actual scalar numeric values for display of min/max/median/mean/etc)
    • logical
    • cellstr
    • table for nested tables, sheesh
      • maybe this is a wrapper around octave.table.internal.TableSummary?
      • do we recursively display the full indented table summary for the nested table, or just a top-level summary? See Nested table support #22 (“nested table support”).
    • datetime
      • harder because datetime itself is not implemented yet
    • categorical
      • harder because categorical itself is not implemented yet
  • will need a generic one that just contains a dumb single-string summary of the variable