Go有几种数据类型

// int8 is the set of all signed 8-bit integers.
// Range: -128 through 127.
type int8 int8

// int16 is the set of all signed 16-bit integers.
// Range: -32768 through 32767.
type int16 int16

// int32 is the set of all signed 32-bit integers.
// Range: -2147483648 through 2147483647.
type int32 int32

// int64 is the set of all signed 64-bit integers.
// Range: -9223372036854775808 through 9223372036854775807.
type int64 int64

// uint8 is the set of all unsigned 8-bit integers.
// Range: 0 through 255.
type uint8 uint8

// uint16 is the set of all unsigned 16-bit integers.
// Range: 0 through 65535.
type uint16 uint16

// uint32 is the set of all unsigned 32-bit integers.
// Range: 0 through 4294967295.
type uint32 uint32

// uint64 is the set of all unsigned 64-bit integers.
// Range: 0 through 18446744073709551615.
type uint64 uint64

// byte is an alias for uint8 and is equivalent to uint8 in all ways. It is
// used, by convention, to distinguish byte values from 8-bit unsigned
// integer values.
type byte = uint8

// rune is an alias for int32 and is equivalent to int32 in all ways. It is
// used, by convention, to distinguish character values from integer values.
type rune = int32

// int is a signed integer type that is at least 32 bits in size. It is a
// distinct type, however, and not an alias for, say, int32.
type int int

// uint is an unsigned integer type that is at least 32 bits in size. It is a
// distinct type, however, and not an alias for, say, uint32.
type uint uint

// float32 is the set of all IEEE-754 32-bit floating-point numbers.
type float32 float32

// float64 is the set of all IEEE-754 64-bit floating-point numbers.
type float64 float64

// complex64 is the set of all complex numbers with float32 real and
// imaginary parts.
type complex64 complex64

// complex128 is the set of all complex numbers with float64 real and
// imaginary parts.
type complex128 complex128

// The complex built-in function constructs a complex value from two
// The complex built-in function constructs a complex value from two
// floating-point values. The real and imaginary parts must be of the same
// size, either float32 or float64 (or assignable to them), and the return
// value will be the corresponding complex type (complex64 for float32,
// complex128 for float64).
func complex(r, i FloatType) ComplexType

// The real built-in function returns the real part of the complex number c.
// The return value will be floating point type corresponding to the type of c.
func real(c ComplexType) FloatType

// The imag built-in function returns the imaginary part of the complex
// number c. The return value will be floating point type corresponding to
// the type of c.
func imag(c ComplexType) FloatType

// bool is the set of boolean values, true and false.
type bool bool

// true and false are the two untyped boolean values.
const (
	true  = 0 == 0 // Untyped bool.
	false = 0 != 0 // Untyped bool.
)

// string is the set of all strings of 8-bit bytes, conventionally but not
// necessarily representing UTF-8-encoded text. A string may be empty, but
// not nil. Values of string type are immutable.
type string string

// iota is a predeclared identifier representing the untyped integer ordinal
// number of the current const specification in a (usually parenthesized)
// const declaration. It is zero-indexed.
const iota = 0 // Untyped int.

a := [2]int{1, 2}
b := [...]int{1, 2}
c := [2]int{1, 3}
fmt.Println(a == b, a == c, b == c) // "true false false"
d := [3]int{1, 2}
fmt.Println(a == d) // compile error: cannot compare [2]int == [3]int

1,
结构体值也可以用结构体面值表示，结构体面值可以指定每个成员的值。

type Point struct{ X, Y int }
p := Point{1, 2}

2,
以成员名字和相应的值来初始化，可以包含部分或全部的成员，

anim := gif.GIF{LoopCount: nframes}

在这种形式的结构体面值写法中，如果成员被忽略的话将默认用零值。

3,
因为结构体通常通过指针处理，可以用下面的写法来创建并初始化一个结构体变量，并返回结构体的地址：

pp := &Point{1, 2}

它是下面的语句是等价的

pp := new(Point)
*pp = Point{1, 2}

不过&Point{1, 2}写法可以直接在表达式中使用，比如一个函数调用。

type Point struct{ X, Y int }

p := Point{1, 2}
q := Point{2, 1}
fmt.Println(p.X == q.X && p.Y == q.Y) // "false"
fmt.Println(p == q)                   // "false"

var ip *int        /* 指向整型*/  ip是一个指向int类型对象的 指针
var fp *float32    /* 指向浮点型 */  fp是一个指向float32类型对象的 指针

   var a int= 20   /* 声明实际变量 */
   var ip *int        /* 声明指针变量 */

   ip = &a  /* 指针变量的存储地址 */

   fmt.Printf("a 变量的地址是: %x\n", &a  )

   /* 指针变量的存储地址 */
   fmt.Printf("ip 变量储存的指针地址: %x\n", ip )

   /* 使用指针访问值 */
   fmt.Printf("*ip 变量的值: %d\n", *ip )

type slice struct {
	array unsafe.Pointer
	len   int
	cap   int
}

// The len built-in function returns the length of v, according to its type:
//	Array: the number of elements in v.
//	Pointer to array: the number of elements in *v (even if v is nil).
//	Slice, or map: the number of elements in v; if v is nil, len(v) is zero.
//	String: the number of bytes in v.
//	Channel: the number of elements queued (unread) in the channel buffer;
//	         if v is nil, len(v) is zero.
// For some arguments, such as a string literal or a simple array expression, the
// result can be a constant. See the Go language specification's "Length and
// capacity" section for details.
func len(v Type) int

// The cap built-in function returns the capacity of v, according to its type:
//	Array: the number of elements in v (same as len(v)).
//	Pointer to array: the number of elements in *v (same as len(v)).
//	Slice: the maximum length the slice can reach when resliced;
//	if v is nil, cap(v) is zero.
//	Channel: the channel buffer capacity, in units of elements;
//	if v is nil, cap(v) is zero.
// For some arguments, such as a simple array expression, the result can be a
// constant. See the Go language specification's "Length and capacity" section for
// details.
func cap(v Type) int

// The append built-in function appends elements to the end of a slice. If
// it has sufficient capacity, the destination is resliced to accommodate the
// new elements. If it does not, a new underlying array will be allocated.
// Append returns the updated slice. It is therefore necessary to store the
// result of append, often in the variable holding the slice itself:
//	slice = append(slice, elem1, elem2)
//	slice = append(slice, anotherSlice...)
// As a special case, it is legal to append a string to a byte slice, like this:
//	slice = append([]byte("hello "), "world"...)
func append(slice []Type, elems ...Type) []Type

// The make built-in function allocates and initializes an object of type
// slice, map, or chan (only). Like new, the first argument is a type, not a
// value. Unlike new, make's return type is the same as the type of its
// argument, not a pointer to it. The specification of the result depends on
// the type:
//	Slice: The size specifies the length. The capacity of the slice is
//	equal to its length. A second integer argument may be provided to
//	specify a different capacity; it must be no smaller than the
//	length. For example, make([]int, 0, 10) allocates an underlying array
//	of size 10 and returns a slice of length 0 and capacity 10 that is
//	backed by this underlying array.
//	Map: An empty map is allocated with enough space to hold the
//	specified number of elements. The size may be omitted, in which case
//	a small starting size is allocated.
//	Channel: The channel's buffer is initialized with the specified
//	buffer capacity. If zero, or the size is omitted, the channel is
//	unbuffered.
func make(t Type, size ...IntegerType) Type

// The new built-in function allocates memory. The first argument is a type,
// not a value, and the value returned is a pointer to a newly
// allocated zero value of that type.
func new(Type) *Type

// The copy built-in function copies elements from a source slice into a
// destination slice. (As a special case, it also will copy bytes from a
// string to a slice of bytes.) The source and destination may overlap. Copy
// returns the number of elements copied, which will be the minimum of
// len(src) and len(dst).
func copy(dst, src []Type) int

// The delete built-in function deletes the element with the specified key
// (m[key]) from the map. If m is nil or there is no such element, delete
// is a no-op.
func delete(m map[Type]Type1, key Type)

创建map：
1，
内置的make函数可以创建一个map：

ages := make(map[string]int) // mapping from strings to ints

2，
我们也可以用map字面值的语法创建map，同时还可以指定一些最初的key/value：

ages := map[string]int{
    "alice":   31,
    "charlie": 34,
}
这相当于

ages := make(map[string]int)
ages["alice"] = 31
ages["charlie"] = 34
因此，另一种创建空的map的表达式是map[string]int{}。

Map中的元素通过key对应的下标语法访问：
ages["alice"] = 32

delete(ages, "alice") // remove element ages["alice"]

所有这些操作是安全的，即使这些元素不在map中也没有关系；
如果一个查找失败将返回value类型对应的零值，例如，
即使map中不存在“bob”下面的代码也可以正常工作，因为ages["bob"]失败时将返回0。
ages["bob"] = ages["bob"] + 1 // happy birthday!

遍历map

for name, age := range ages {
    fmt.Printf("%s\t%d\n", name, age)
}

func name(parameter-list) (result-list) {
    body
}

使用内置的make函数，我们可以创建一个channel：

使用内置的make函数，我们可以创建一个channel：

ch := make(chan int) // ch has type 'chan int'