Golang Notes - 6

Data Types

predeclared types - builtin types

• basic types: integers , floating point numbers, complex numbers, byte, rune, string, boolean

• int8, int16, int32, int64,
  int -> alias for int32 or int64 based on platform
  

var i8 int8 = -128 // [-128, 127]
var ui16 uint16 = 65535 // [0, 65535]

• uint8, uint16, uint32, uint64, uint -> alias for uint32 or uint64 based on platform
• float32, float64
• complex64, complex128

comp1 := complex(1, 2) // constructor way
comp2 := 1 + 2i    // second way to init

• byte -> alias for uint8
• rune -> alias for int32 represents a Unicode code point

var r rune = 'f'
fmt.Printf("%T\n", r)
// int32

• bool type - pre-defined constants true and false

• string type

  • unicode chars written enclosed by double-quote

• composite types : array, slice, map, struct, pointer, function, interface, channel

• array type

  • fixed length
  • must contain single type

var nums = [3]int{1,2,3}

• slice type
  • dynamic length, can shrink or grow
  • must contain same type

var cities = []string{"Istanbul", "Tokyo"}

• map type
  • unordered group of elements of single type
  • indexed by a set of unique keys

balances := map[string]float64{
"USD": 2000.3,
"EUR": 3000.4,
}

• struct type
  • consist of named elements, fields
  • each field has name and type
  • allow user to define custom type

type Person struct {
  name string
  age int
}

• pointer type
  • stores memory address
  • uninitialized, default value nil

var x int = 1
ptr := &x // address of x
fmt.Printf("%T\n", ptr)
fmt.Println(ptr)
fmt.Println(*ptr) // access value
// *int
// 0xc000012028
// 1

• function type

func f() {}
fmt.Printf("%T\n", f)
// func()

• interface type
• channel type
  • provides mechanism for concurrent communication

c := make(chan int) // unbuffered
c2 := make(chan int, 2) // buffered
fmt.Printf("%T\n", c)
// chan int