Golang Learning notes 2--types and variables

This is a creation in Article, where the information may have evolved or changed.

1. Basic types

type	length	Default Value	Description
bool	1	False	Cannot use 0, 1 instead of false, true
Byte	1	0	Equivalent to Uint8
int, UINT	4, 8	0	Default integer type, based on platform, 32 or 64 bits
int8, Uint8	1	0	-128 ~ 127,0 ~ 255
Int16, UInt16	2	0	-32768 ~ 32767,0 ~ 65535
Int32, UInt32	4	0	-(2^32/2) ~ (2^32/2-1), 0 ~ 2^32
Int64, UInt64	8	0	-(2^64/2) ~ (2^64/2-1), 0 ~ 2^64
Float32	4	0.0
Float64	8	0.0	Default floating-point number type
Complex64	8
complex128	16
Rune	4	0	Unicode Code Point, Int32
UIntPtr	4,8	0	UINT sufficient to store pointers
String		""	String, default value is an empty string, NOT NULL
Array			Array
struct			Structural body
function		Nil	Function
Interface		Nil	Interface
Map		Nil	Dictionary, reference type
Slice		Nil	Slices, reference types
Channel		Nil	Channel, reference type

2. Type aliases

Setting the type alias can make the code more readable, and at a glance what this variable does:

type (    int64)

3. Declaration and assignment of variables

• Declaration of variable: var a int
• Assignment of a variable: a = 123
• Declare and assign a value: var a int = 123 (if the type is omitted, the compiler automatically infers the type based on the value)
• Declaration of multiple variables

Parallel mode (can omit type, deduced by value)

varint123

The shorthand form for declaring variables inside a function:

funciont main(){    1}

The return value can be ignored with "_" When the function returns multiple values

134

4. Type conversion

• There is no implicit conversion in go, all type conversions must show a declaration
• Conversions can only occur between two mutually compatible types
• Format for type conversions:

varfloat321.1int(a)

• Grammatical ambiguity

If the target of the transformation is a pointer, a one-way channel, or a function type that does not have a return value, then parentheses must be used to avoid parsing a syntax error.

fun main() {    100    p := *int(&x)   //错误:cannot convert &x (type *int) to type int                    //    invalid indirect of int(&x) (type int)    fmt.Println(p)}

The correct approach is to use parentheses so that the compiler will *int parse the pointer type.

(*int)(p)(<-chanint)(c)(func())(x)