@thi.ng/grid-iterators/diagonal-slope.js

2D grid and shape iterators w/ multiple orderings

import { assert } from "@thi.ng/errors/assert";
import { __opts } from "./utils.js";
function* diagonalSlopeY(opts) {
  const { cols, rows, tx } = __opts(opts);
  const maxX = cols - 1;
  const slope = opts.slope | 0;
  assert(slope > 0, "slope must be > 0");
  const num = cols * rows - 1;
  let x = 0;
  let y = 0;
  let nx = Math.min(1, maxX);
  let ny = nx > 0 ? 0 : slope;
  let n = slope;
  const reset = () => {
    n = slope;
    x = nx;
    y = ny;
    if (nx < maxX) nx++;
    else ny += slope;
  };
  for (let i = 0; i <= num; i++) {
    yield tx(x, y);
    if (--n > 0) {
      y++;
      if (y >= rows) reset();
    } else {
      x--;
      y++;
      if (x < 0 || y >= rows) reset();
      else n = slope;
    }
  }
}
function* diagonalSlopeX(opts) {
  const { cols, rows, tx } = __opts(opts);
  const maxX = cols - 1;
  const slope = opts.slope | 0;
  assert(slope > 0, "slope must be > 0");
  const num = cols * rows - 1;
  let x = Math.min(slope - 1, maxX);
  let y = 0;
  let n = x + 1;
  let nx = Math.min(x + slope, maxX);
  let ny = nx > 0 ? 0 : slope;
  const reset = () => {
    x = nx;
    y = ny;
    if (nx < maxX) {
      nx = Math.min(nx + slope, maxX);
      n = slope;
    } else {
      ny++;
      n = x % slope + 1;
    }
  };
  for (let i = 0; i <= num; i++) {
    yield tx(x, y);
    if (--n > 0) {
      x--;
      if (x < 0) reset();
    } else {
      x--;
      y++;
      if (x < 0 || y >= rows) reset();
      else n = slope;
    }
  }
}
export {
  diagonalSlopeX,
  diagonalSlopeY
};