rstiller · September 28, 2018 07:43 · Sep 28, 2018
diff --git a/test.js b/test.js
@@ -0,0 +1,78 @@
+/*
+ streaming cartesian product elements uses less memory ...
+*/
+const generator = cartesianProductSimplified(['a', 'b'], [1, 2, 3, 4], ['x', 'y', 'z']);
+/* prints
+[ 'a', 1, 'x' ]
+[ 'a', 1, 'y' ]
+[ 'a', 1, 'z' ]
+[ 'a', 2, 'x' ]
+[ 'a', 2, 'y' ]
+[ 'a', 2, 'z' ]
+[ 'a', 3, 'x' ]
+[ 'a', 3, 'y' ]
+[ 'a', 3, 'z' ]
+[ 'a', 4, 'x' ]
+[ 'a', 4, 'y' ]
+[ 'a', 4, 'z' ]
+[ 'b', 1, 'x' ]
+[ 'b', 1, 'y' ]
+[ 'b', 1, 'z' ]
+[ 'b', 2, 'x' ]
+[ 'b', 2, 'y' ]
+[ 'b', 2, 'z' ]
+[ 'b', 3, 'x' ]
+[ 'b', 3, 'y' ]
+[ 'b', 3, 'z' ]
+[ 'b', 4, 'x' ]
+[ 'b', 4, 'y' ]
+[ 'b', 4, 'z' ]
+*/
+printValues(generator);
+
+// helper function to print all values from a generator function
+function printValues(generator) {
+    let iteration = null;
+    while (iteration = generator.next()) {
+        if (iteration.done === true) {
+            break;
+        }
+        console.log(iteration.value);
+    }
+}
+
+// helper function to construct the arguments array for the 'cartesianProduct' class
+function cartesianProductSimplified(...arrays) {
+    let args = [];
+    for (let i = 1; i < arrays.length; i++) {
+        args = args.concat([cartesianProduct, arrays[i]]);
+    }
+    args.splice(0, 0, arrays[0]);
+    return cartesianProduct(...args);
+}
+
+/*
+ call it like this:
+ 
+ cartesianProduct(['a', 'b'], cartesianProduct, [1, 2, 3, 4], cartesianProduct, ['x', 'y', 'z']);
+ 
+ use cartesianProductSimplified to simplify it:
+ 
+ cartesianProductSimplified(['a', 'b'], [1, 2, 3, 4], ['x', 'y', 'z'])
+*/
+function* cartesianProduct(values, generator, ...generatorArgs) {
+    for (const value of values) {
+        if (generator) {
+            const iterator = generator(...generatorArgs);
+            let iteration = null;
+            while (iteration = iterator.next()) {
+                if (iteration.done === true) {
+                    break;
+                }
+                yield [value, ...iteration.value];
+            }
+        } else {
+            yield [value];
+        }
+    }
+}