30日の行く:日2と3

どうやって

2日目

データ構造

アレイ

var array [40]int

// Declare and initialize
array2 := [5]int{1, 3, 4, 5, 6}

// Access an index in the array
fmt.Println(array[20])

// add something to an index in the array
array[10] = 300

// get the size of the array
fmt.Println(len(array))

var twoD [4][9]int
for i := 0; i < 4; i++ {
    for j := 0; j < 9; j++ {
 twoD[i][j] = i + 
    }
}

スライス

// Create a slice pass the type and initial size to make
sl := make([]string, 3)

// Declaring and initializing a slice
t := []string{"ab", "bc", "cd"}

// Access an item in a slice
fmt.Println(sl[2])

// set an index in a slice
sl[1] = "Hello"

sl = append(sl, "new")

// Create a new slice with the length of the slice you want to copy
c := make([]string, len(sl))
// copies sl into c
copy(c, sl)

// creates a nes slice from index 1 to 2
newSlice := sl[1:3]
// creates slice from index 0 to 3 (excluding 4)
newSlice = sl[:4]
// slice from index 2 to the last one
newSlice = sl[2:]

twoD := make([][]int, 3)
for i := 0; i < 3; i++ {
    innerLen := i + 1
    twoD[i] = make([]int, innerLen)
    for j := 0; j < innerLen; j++ {
 twoD[i][j] = i + j
    }
}

// result = [[0] [1 2] [2 3 4]]

マップ

m := make(map[string]int)

// declare and initialize a map
m2 := map[string]int{"foo": 4, "bar": 40}

// set key/value pairs
m["one"] = 2
m["two"] = 3

// get a value with a key
v := m["one"]

// get number of key/value pairs
fmt.Println(len(m))

// To delete a key value pair use builtin function
delete(m, "two")

_, prs := m["two"]

範囲

// array, slices
for index, value := range array {
    fmt.Println(value)
}

//map 
for key, value := range exMap {
    fmt.Printf("%s -> %s\n", key, value)
}

// iterate over map keys only
for key := range exMap {
    fmt.Println(key)
}

// iterate over strings
for index, ru := range "Golang" {
    fmt.Println(ru)
}

3日目

関数

// function structure
// function name(arguments) return type {}
func sayHello(name string) string {
    return "Hello " + name 
}
// call the function sayHello("Kacha")

// function with multiple return values
func names() (string, string) {
    return "Scott", "Ramona"
}

// variadic function
func add(nums ...int) {
    total := 0
    for _, num := range nums {
 total += num
    }
    return total
}

...