3.Basic Data Types

Integer

There are two major groups of integer:

• signed:
  • int8
  • int16
  • int32
  • int64
• unsigned
  • uint8
  • uint16
  • uint32
  • uint64

Type	Description
uint8	unsinged 8 byte (0 ~ 255)
uint16	unsinged 16 byte (0 ~ 65535)
uint32	unsigned 32 byte (0 ~ 4294967295)
uint64	unsigned 64 byte (0 ~ 18446744073709551615)
int8	signed 8 byte (-128 ~ 127)
int16	signed 16 byte (-32768 ~ 32767)
int32	signed 32 byte (-2147483648 ~ 2147483647)
int64	signed 64 byte (-9223372036854775808 ~ 9223372036854775807)

special integer

Type	Description
uint	in 32-byte system is uint32, in 64-byte system is uint64
int	in 32-byte system is int32, in 64-byte system is int64
uintptr	unsigned integer, use for saving a pointer

Octal & Hexadecimal

in Go you can not define binary integer directly

package main

import "fmt"

func main(){
    var a int = 10
    fmt.Printf("%d \n", a) // 10
    fmt.Printf("%b \n", a) // 1010 binary
    
    var b int = 077
    
}

Float

In Go has float32and float64. According to the IEEE 754 standard: the range of float32 is 3.4e38 math.MaxFloat32 . float64 has range 1.8e308 math.MaxFloat64 .

use the following code to print:

fm.Printf("%f\n", math.pi)
fm.Printf("%.2f\n", math.pi)

by default the float is float64

f1 := 1.23456
fmt.Printf("%T", f1) // by default the decimal is float64

Complex

complex64 and complex128

var c1 complex64
c1 = 1 + 2i
var c2 complex128
c2 = 2 + 3i
fmt.Println(c1)
fmt.Println(c2)

Boolean

Go use bool to determine Boolean data type only has true and false two values

Note:

1. The default value of bool is false
2. Go not allowed transfer other data type into bool
3. can not use fool for numerical operations

String

String is a basic data type in the go language, use UTF-8 format. value is the content inside of the double quotes("), you can use no ASCII character directly, such as:

s1 := "Hello"
s2 := "你好"

character use single quote('), such as:

c1 := 'h'
c2 := '你'

// 1 byte = 8 bit
// 1 char 'A' = 1 byte
// 1 utf-8 letter '你' = 3 byte

Escape code

Escape code	Meaning
\r	Carriage return
\n	Newline
\t	Tabs
\'	Single quote
\"	Double quotes
\\	Backslash

Multiline string

In go if you want to determine a multiline string you need to use Backticks, such as:

str := `First line
Second line
Third line
`
fmt.Println(str)

Line breaks between backticks will be regarded as line breaks in the string, but all escape characters are invalid, and the text will be output as it is.

Common methods of strings

Method	Description
len(str)	get the length of the string
+ or fmt.Sprintf()	Concatenated string
strings.Split()	Split string
strings.contains()	check if string contain certain string
strings.HasPrefix(), strings.HasSuffix()	check if has Pre\Suffix
strings.Index(), strings.LastIndex()	where the substring appears
strings.Join(a[] string, sep string)	Join strings into a string

byte and rune