arrays: implement python-inspired array zip function and test (#8667)

vlib/arrays/arrays.v

@@ -98,6 +98,33 @@ pub fn merge<T>(a []T, b []T) []T {
 	return m
 }
 
+// group n arrays into a single array of arrays with n elements
+pub fn group<T>(lists ...[]T) [][]T {
+	mut length := if lists.len > 0 { lists[0].len } else { 0 }
+	// calculate length of output by finding shortest input array
+	for ndx in 1 .. lists.len {
+		if lists[ndx].len < length {
+			length = lists[ndx].len
+		}
+	}
+
+	if length > 0 {
+		mut arr := [][]T{cap: length}
+		// append all combined arrays into the resultant array
+		for ndx in 0 .. length {
+			mut zipped := []T{cap: lists.len}
+			// combine each list item for the ndx position into one array
+			for list_ndx in 0 .. lists.len {
+				zipped << lists[list_ndx][ndx]
+			}
+			arr << zipped
+		}
+		return arr
+	}
+
+	return [][]T{}
+}
+
 [deprecated]
 pub fn shuffle<T>(mut a []T, n int) {
 	panic('Please use rand.util.shuffle() instead')

vlib/arrays/arrays_test.v

@@ -52,3 +52,36 @@ fn test_merge() {
 	assert merge<int>(a, c) == a
 	assert merge<int>(d, b) == b
 }
+
+fn test_fixed_array_assignment() {
+	mut a := [2]int{}
+	a[0] = 111
+	a[1] = 222
+	b := a
+	assert b[0] == a[0]
+	assert b[1] == a[1]
+	mut c := [2]int{}
+	c = a
+	assert c[0] == a[0]
+	assert c[1] == a[1]
+	d := [3]int{init: 333}
+	for val in d {
+		assert val == 333
+	}
+	e := [3]string{init: 'vlang'}
+	for val in e {
+		assert val == 'vlang'
+	}
+}
+
+fn test_group() {
+	x := [4, 5, 6]
+	y := [2, 1, 3]
+
+	z := group<int>(x, y)
+	assert z == [[4, 2], [5, 1], [6, 3]]
+	x2 := [8, 9]
+	z2 := group<int>(x2, y)
+	assert z2 == [[8, 2], [9, 1]]
+	assert group<int>(x, []int{}) == [][]int{}
+}