Include type definitions

[estollnitz]

Type definitions for the FOLD library would allow for static type checking as well as intellisense in code editors. This could be accomplished either by providing a .d.ts type definition file for the existing code, or by implementing FOLD in TypeScript.

[mayakraft]

just worked on a Swift project where i had to define the structure like this. it got me thinking about which entries inside the arrays are allowed to be null/undefined. referring to the 2.0 feature strict null checks. also can relate this to the new 1.2 spec #30 which makes a point that 3 arrays allow null values.

here is the swift definition. the way swift works is anything followed by a ? can be undefined (nil). so [String]? is an array which may not exist (null) but its contents MUST be a string, where [Double?]? means the array might not exist, and it can include nulls. in the case of FOLD, all top-level entries end with ? because nothing is required (although file_spec might be the closest to "required").

the entries which allow null are currently: edges_faces and vertices_faces and faces_faces, as mentioned in #30 , i think i remember seeing null inside edges_foldAngle exported from Origami Simulator. is that correct, and a behavior ? edges_assignment literally has an undefined (unassigned) type so i wonder if we can say no null values in that array.

here i have file_frames defined recursively, but i expect that to be incorrect. file_frames's type should be similar to FOLD, but exclude some things, like a recursive file_frames, and probably also exclude any file_ entries, but allow frame_ entries. does that sound about right?

struct FOLD: Decodable {
  let vertices_coords: [[Double]]?
  let vertices_vertices: [[Int]]?
  let vertices_edges: [[Int]]?
  let vertices_faces: [[Int?]]?
  let edges_vertices: [[Int]]?
  let edges_assignment: [String]?
  let edges_foldAngle: [Double?]?
  let edges_faces: [[Int?]]?
  let faces_vertices: [[Int]]?
  let faces_edges: [[Int]]?
  let faces_faces: [[Int?]]?
  let file_frames: [FOLD]?

  // metadata
  let file_spec: Double?
  let file_creator: String?
  let file_author: String?
  let file_title: String?
  let file_description: String?
  let file_classes: [String]?
  let frame_author: String?
  let frame_title: String?
  let frame_description: String?
  let frame_unit: String?
  let frame_classes: [String]?
  let frame_attributes: [String]?
}

[qurben]

This would be really useful. When implementing FOLD in java with just the spec it was sometimes hard to understand what the exact type of a field would be as the spec doesn't differentiate between different kinds of numbers.