Utility functions for constructing and keeping references of objects.
Useful for Ease of comparison with reference equality ===.
Usage
Let's say you have these types:
type Color = 'w' | 'b'; type Role = 'b' | 'n' | 'k' | 'q';
type Piece = { color: Color, role: Role }
let colors = ['w', 'b']; let roles = ['b', 'n', 'k', 'q'];
You have a constructor function
const piece = (color: Color, role: Role): Piece => ({ color, role });
You want to construct and reference any possible piece like this:
let pieces = bd.DB2<Color, Role, Piece>(piece, colors, roles);
pieces.get('w', 'n') === pieces.get('w', 'n'); // true