03-array,map,strings

Array - fixed sized, cannot be expanded, default initialized to [0,...]

var arr [3]int // default [0,0,0]
arr[0] // 0
arr[0] = 1 // [1,0,0]

Slicing the array

oneTwo := arr[0:2]

Slice - similar to array, more flexible, can be expanded

slice := []int{1,2,3}
slice = append(slice, 4) // adding an element

Map - similar to dictionary

myMap = make(map[string]int) // declare a map with key of string and value of int

Setting and indexing map

myMap['exist'] // get the value
myMap['exist'] = 10 // setting the value (only int allowed)
myMap['notexist'] // still returns the default value

Checking if something is found

value, ok := myMap['notexist']
if ok {} // only if the value exists

• Zero value for map: If you don’t initialize a map, its zero value is nil. You cannot add elements to a nil map. You must use make or a map literal to initialize it.

    var nilMap map[string]int // nilMap is nil
    // nilMap["key"] = 10 // This would panic!
 
    initializedMap := make(map[string]int)
    initializedMap["key"] = 10 // This is fine.

Iterating over array, slices, map
For loop syntax

for i := 0; i<len(arr); i++ {}

Consists of initialization, condition, post

• init, the starting value
• condition, will continue if met
• post: after the loop (increment by 1)

Iterating keys of the map

for k, v := range(myMap) {}

Strings

• in Go, strings are UTF-8, and indexed characters may be different

myStr := "Hello World"
myStr[0] // return the UTF-8 value of H

Runes - like characters, but represent a Unicode code point

var r rune = 'a'
[]rune('Hello World')[0] // H

String Builder, requires the strings import

sb := strings.Builder
sb.WriteString("a")
sb.String() // a