@thi.ng/grid-iterators/diamond-square.js

2D grid and shape iterators w/ multiple orderings

import { defBitField } from "@thi.ng/bitfield/bitfield";
function* diamondSquare(exp) {
  const size = 1 << exp;
  const size1 = size + 1;
  const s2 = size >> 1;
  let res = size;
  const idx = defBitField(size1 * size1);
  const acc = [];
  const $ = (x, y) => {
    !idx.setAt(x + y * size1) && acc.push([x, y]);
  };
  $(0, 0);
  $(res, 0);
  $(res, res);
  $(0, res);
  yield* acc;
  while (res > 1) {
    const r2 = res >> 1;
    for (let y = 0; y <= s2; y += res) {
      const y1 = y + r2;
      const y2 = y + res;
      for (let x = r2; x <= s2; x += res) {
        acc.length = 0;
        const x1 = x - r2;
        const x2 = x + r2;
        $(x, y);
        $(size - x, y);
        $(size - x, size - y);
        $(x, size - y);
        $(x2, y1);
        $(size - x2, y1);
        $(size - x2, size - y1);
        $(x2, size - y1);
        $(x, y2);
        $(size - x, y2);
        $(size - x, size - y2);
        $(x, size - y2);
        $(x1, y1);
        $(size - x1, y1);
        $(size - x1, size - y1);
        $(x1, size - y1);
        $(x, y1);
        $(size - x, y1);
        $(size - x, size - y1);
        $(x, size - y1);
        yield* acc;
      }
    }
    res = r2;
  }
}
export {
  diamondSquare
};