feat(grid-iterators): add interleave fns

packages/grid-iterators/src/columns.ts

@@ -1,6 +1,6 @@
 /**
- * Yields sequence of 2D grid coordinates in zigzag column order starting
- * from [0,0], given `cols` and `rows`.
+ * Yields sequence of 2D grid coordinates in zigzag column order
+ * starting from [0,0], given `cols` and `rows`.
  *
  * Ported & modified from original Java code by Christopher Kulla.
  * https://sourceforge.net/p/sunflow/code/HEAD/tree/trunk/src/org/sunflow/core/bucket/SpiralBucketOrder.java

packages/grid-iterators/src/diagonal.ts

@@ -1,6 +1,7 @@
 /**
  * Yields sequence of 2D grid coordinates in diagonal order starting at
- * [0,0] and using given `cols` and `rows`.
+ * [0,0] and using given `cols` and `rows`. Each diagonal starts at y=0
+ * and progresses in -x,+y direction.
  *
  * Ported & modified from original Java code by Christopher Kulla.
  * https://sourceforge.net/p/sunflow/code/HEAD/tree/trunk/src/org/sunflow/core/bucket/DiagonalBucketOrder.java

packages/grid-iterators/src/index.ts

@@ -1,6 +1,7 @@
 export * from "./columns";
 export * from "./diagonal";
 export * from "./hilbert";
+export * from "./interleave";
 export * from "./random";
 export * from "./rows";
 export * from "./spiral";

packages/grid-iterators/src/interleave.ts

@@ -0,0 +1,43 @@
+import { map, range2d } from "@thi.ng/transducers";
+
+/**
+ * Yields 2D grid coordinates in the order of interleaved columns with
+ * configurable `step` size (default: 2). I.e. returns columns in this
+ * order:
+ *
+ * - 0, step, 2 * step, 3 * step...
+ * - 1, 2 * step + 1, 3 * step + 1...
+ * - etc.
+ *
+ * @see interleaveRows2d
+ *
+ * @param cols
+ * @param rows
+ * @param step
+ */
+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));
+    }
+}
+
+/**
+ * Similar to `interleaveColumns2d`, but yields 2D grid coordinates in
+ * the order of interleaved rows with configurable `step` size (default:
+ * 2). I.e. returns rows in this order:
+ *
+ * - 0, step, 2 * step, 3 * step...
+ * - 1, 2 * step + 1, 3 * step + 1...
+ * - etc.
+ *
+ * @see interleaveColumns2d
+ *
+ * @param cols
+ * @param rows
+ * @param step
+ */
+export function* interleaveRows2d(cols: number, rows = cols, step = 2) {
+    for (let j = 0; j < step; j++) {
+        yield* range2d(0, cols, j, rows, 1, step);
+    }
+}

packages/grid-iterators/src/zcurve.ts

@@ -2,10 +2,10 @@ import { ceilPow2 } from "@thi.ng/binary";
 import { demux2 } from "@thi.ng/morton";
 
 /**
- * Yields grid coordinates in Z-curve (Morton) order. A perfect Z-curve
- * is only generated if `cols` AND `rows` are equal and a power of 2.
- * Due to using 32bit morton codes, only supports grid sizes up to 32767
- * (0x7fff) in either dimension.
+ * Yields 2D grid coordinates in Z-curve (Morton) order. A perfect
+ * Z-curve is only generated if `cols` AND `rows` are equal and a power
+ * of 2. Due to using 32bit morton codes, only supports grid sizes up to
+ * 32767 (0x7fff) in either dimension.
  *
  * @param cols
  * @param rows