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2D Slices and ArraysRepresent multiple dimensions by nesting slices and arrays. Learn 2D slice syntax.
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This page was last reviewed on Apr 21, 2023.
2D slice, array. In the Go language we model 2D things with slices of slices. In the 2 levels of nesting we store the 2 dimensions.
Shows a 2d slice
Appending data. To create a 2D slice, we use append() to add each row. Then we can access the data by indexing through the slices.
Slice example. Consider a slice of slices: we could use the term "jagged" to describe nested slices. Each sub-slice can be any number of elements long.
Slice
Step 1 Initially we create an empty slice of slices—it has no top-level slice elements.
Step 2 Here we create 2 rows (which are also slices). And with append() we add the two rows to the "values."
Step 3 We can access entire rows with the first index. Row 0 is the first row, and row 1 is the second row.
Step 4 With 2 indexes, we address a single int element. We can get or set an integer in the nested slices.
Shows a 2d slice
package main import "fmt" func main() { // Step 1: create empty collection. values := [][]int{} // Step 2: these are the first two rows. // ... Append each row to the two-dimensional slice. row1 := []int{1, 2, 3} row2 := []int{4, 5, 6} values = append(values, row1) values = append(values, row2) // Step 3: display first row, and second row. fmt.Println("Row 1") fmt.Println(values[0]) fmt.Println("Row 2") fmt.Println(values[1]) // Step 4: access an element. fmt.Println("First element") fmt.Println(values[0][0]) }
Row 1 [1 2 3] Row 2 [4 5 6] First element 1
2D arrays. To create a 2D array we must specify each dimension. We can then assign individual elements within the array. Here we create a 2 by 2 array of strings.
Tip Arrays in Go have fixed sizes. We must specify the size of the array. For variable-size collections, slices are better.
package main import "fmt" func main() { // Create two-dimensional array. letters := [2][2]string{} // Assign all elements in 2 by 2 array. letters[0][0] = "a" letters[0][1] = "b" letters[1][0] = "c" letters[1][1] = "d" // Display result. fmt.Println(letters) }
[[a b] [c d]]
Nested string slices. Here we use strings in nested slices. Each slice does not have the same length: this is a jagged slice. We loop over the nested slices with for.
Detail The range built-in returns all indexes (in order) of the animals slice. We then access each nested slice of animal names.
for
package main import "fmt" func main() { // Create an empty slice of slices. animals := [][]string{} // Create three string slices. row1 := []string{"fish", "shark", "eel"} row2 := []string{"bird"} row3 := []string{"lizard", "salamander"} // Append string slices to outer slice. animals = append(animals, row1) animals = append(animals, row2) animals = append(animals, row3) // Loop over slices in animals. for i := range animals { fmt.Printf("Row: %v\n", i) fmt.Println(animals[i]) } }
Row: 0 [fish shark eel] Row: 1 [bird] Row: 2 [lizard salamander]
Some data sources are often stored in a two-dimensional plane. This can be efficient. But often, using a map is a good option—it saves space in sparse collections.
A review. Idiomatic Go is code that matches the language's popular usage. In Go we usually prefer slices (not arrays). So a 2D slice is an ideal solution.
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Sam Allen is passionate about computer languages. In the past, his work has been recommended by Apple and Microsoft and he has studied computers at a selective university in the United States.
This page was last updated on Apr 21, 2023 (edit).
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