Slices

Slices are similar to arrays, but offer more powerful ways of dealing with data.

The type of a slice is determined only by the elements it contains, and is independent of the the number of elements in the slice. Slices also support various built-in methods in golang including make, copy, append etc. We will explore some of these methods below.

Slices are similar to C++ vectors in that they can grow and shrink dynamically. We can initialize a string slice below with 4 initial values.

package main

import "fmt"

func main() {
  cars := make([]string, 4)
  fmt.Println("empty slice:", cars)

  cars[0] = "tesla"
  cars[1] = "bmw"
  cars[2] = "honda"
  // print out all the values currently in cars
  fmt.Println(cars)
  fmt.Printf("Third car: %s", s[2])
    
  // the len method works on slices too
  fmt.Println("len:", len(s))
  
  // add new items to the cars slice
  // Note: we need to reassign cars to the value of append
  cars = append(cars, "rivian")
  cars = append(s, "toyota", "buick")
  fmt.Println(cars)
  
  // make a copy of the car slice
  cars_copy := make([]string, len(cars))
  copy(cars_copy, cars)
  fmt.Println(cars_copy)
}

Slices also support "slicing" using a colon symbol. "slicing" here refers to getting only parts of a slice data structure. For example,

package main

import "fmt"

func main() {
  authors := []string {"Hurston", "Artwood", "Didion", "Le Guin", "Morrison", "Walker"}
  // "slicing" takes the format slice[low:high].
  // For example, this gets a slice of the elements
  // authors[2], authors[3], and authors[4].
  some_authors := s[2:5]
  fmt.Println("some authors:", some_authors)
  // slice up to (but excluding) authors[5].
  famous_authors = authors[:5]
  fmt.Println("These authors are famous: ", famous_authors)

  // slice from 3 (inclusive) to the end
  contemporary_authors = authors[3:]
}