uninitialized-var-zero-value.go

package main

import "fmt"

func main() {
	var i int
	var i8 int8
	var i16 int16
	var i32 int32
	var i64 int64

	var u uint
	var u8 uint8
	var u16 uint16
	var u32 uint32
	var u64 uint64

	var uptr uintptr

	var f32 float32
	var f64 float64

	var c64 complex64
	var c128 complex128

	fmt.Println("numeric types (int/uint/uintptr/float/complex):", i, i8, i16, i32, i64, u, u8, u16, u32, u64, uptr, f32, f64, c64, c128)

	var r rune // alias for int32, represents a unicode code point
	fmt.Println("rune:", r)

	var b byte // alias for uint8
	fmt.Println("byte:", b)

	var bl bool
	fmt.Println("boolean:", bl)

	var s string
	fmt.Println("string:", s, "(an empty string)")

	var e error
	fmt.Println("error:", e)

	var p *int
	fmt.Println("pointer:", p)

	var ch chan string
	fmt.Println("channel:", ch)

	var fn func()
	fmt.Println("func:", fn)

	var iface interface{}
	fmt.Println("interface:", iface)

	var m map[string]int
	fmt.Println("map:", m)
	fmt.Println("map variable compared to nil, i.e m == nil: ", m == nil)

	var sl []int
	fmt.Println("slice:", sl)
	fmt.Println("slice variable compared to nil, i.e sl == nil: ", sl == nil)

	var arrInt [5]int
	fmt.Println("array of 5 ints:", arrInt)

	var arrBool [5]bool
	fmt.Println("array of 5 bools:", arrBool)

	var arrStr [5]string
	fmt.Println("array of 5 strings:", arrStr, "(an array of 5 empty strings)")
}

/* Output:
numeric types (int/uint/uintptr/float/complex): 0 0 0 0 0 0 0 0 0 0 0 0 0 (0+0i) (0+0i)
rune: 0
byte: 0
boolean: false
string:  (an empty string)
error: <nil>
pointer: <nil>
channel: <nil>
func: <nil>
interface: <nil>
map: map[]
map variable compared to nil, i.e m == nil:  true
slice: []
slice variable compared to nil, i.e sl == nil:  true
array of 5 ints: [0 0 0 0 0]
array of 5 bools: [false false false false false]
array of 5 strings: [    ] (an array of 5 empty strings)
*/