feat(grid-iterators): add new iterators

- add columns, rows
- add columnEnds, diagonalEnds, rowEnds

packages/grid-iterators/src/column-ends.ts

@@ -0,0 +1,14 @@
+/**
+ * Filtered version of {@link columns2d}, only including end points of
+ * each column.
+ *
+ * @param cols -
+ * @param rows -
+ */
+export function* columnEnds2d(cols: number, rows = cols) {
+    rows--;
+    for (let x = 0; x < cols; x++) {
+        yield [x, 0];
+        yield [x, rows];
+    }
+}

packages/grid-iterators/src/columns.ts

@@ -0,0 +1,11 @@
+import { map, range2d } from "@thi.ng/transducers";
+import { swapxy } from "./swap";
+
+/**
+ * Yields sequence of 2D grid coordinates in column-major order.
+ *
+ * @param cols
+ * @param rows
+ */
+export const columns2d = (cols: number, rows = cols) =>
+    map(swapxy, range2d(rows, cols));

packages/grid-iterators/src/diagonal-ends.ts

@@ -0,0 +1,26 @@
+import { diagonal2d } from "./diagonal";
+
+/**
+ * Filtered version of {@link diagonal2d}, only including end points of
+ * the diagonals, apart from the very first and last points: `[0,0]` and
+ * `[cols-1, rows-1]`.
+ *
+ * @remarks
+ * `cols` and `rows` MUST be both >= 2.
+ *
+ * @param cols -
+ * @param rows -
+ */
+export function* diagonalEnds2d(cols: number, rows = cols) {
+    const num = cols * rows - 1;
+    const maxX = cols - 1;
+    const maxY = rows - 1;
+    let i = 0;
+    for (let p of diagonal2d(cols, rows)) {
+        if (i > 0 && i < num) {
+            const [x, y] = p;
+            if (x === 0 || x === maxX || y === 0 || y === maxY) yield p;
+        }
+        i++;
+    }
+}

packages/grid-iterators/src/index.ts

@@ -1,10 +1,15 @@
 export * from "./circle";
+export * from "./column-ends";
+export * from "./columns";
 export * from "./diagonal";
+export * from "./diagonal-ends";
 export * from "./hilbert";
 export * from "./hvline";
 export * from "./interleave";
 export * from "./line";
 export * from "./random";
+export * from "./row-ends";
+export * from "./rows";
 export * from "./spiral";
 export * from "./zcurve";
 export * from "./zigzag-columns";

packages/grid-iterators/src/interleave.ts

@@ -1,4 +1,5 @@
 import { map, range2d } from "@thi.ng/transducers";
+import { swapxy } from "./swap";
 
 /**
  * Yields 2D grid coordinates in the order of interleaved columns with
@@ -17,7 +18,7 @@ import { map, range2d } from "@thi.ng/transducers";
  */
 export function* interleaveColumns2d(cols: number, rows = cols, step = 2) {
     for (let j = 0; j < step; j++) {
-        yield* map((p) => [p[1], p[0]], range2d(0, rows, j, cols, 1, step));
+        yield* map(swapxy, range2d(0, rows, j, cols, 1, step));
     }
 }
 

packages/grid-iterators/src/row-ends.ts

@@ -0,0 +1,14 @@
+/**
+ * Filtered version of {@link rows2d}, only including end points of
+ * each row.
+ *
+ * @param cols -
+ * @param rows -
+ */
+export function* rowEnds2d(cols: number, rows = cols) {
+    cols--;
+    for (let y = 0; y < rows; y++) {
+        yield [0, y];
+        yield [cols, y];
+    }
+}

packages/grid-iterators/src/rows.ts

@@ -0,0 +1,10 @@
+import { range2d } from "@thi.ng/transducers";
+
+/**
+ * Yields sequence of 2D grid coordinates in row-major order. Same as
+ * {@link @thi.ng/transducers#range2d}.
+ *
+ * @param cols
+ * @param rows
+ */
+export const rows2d = (cols: number, rows = cols) => range2d(cols, rows);

packages/grid-iterators/src/swap.ts

@@ -0,0 +1,13 @@
+/**
+ * Swaps XY in-place.
+ *
+ * @param p
+ *
+ * @internal
+ */
+export const swapxy = (p: number[]) => {
+    const t = p[0];
+    p[0] = p[1];
+    p[1] = t;
+    return p;
+};