Basic ❶

I'm going to write the understanding of Go from the basics of programming!

What is a character string?

package main
func main(){
  println("Hello, Go")
}

Error occurs if not enclosed in "" (double quotes)

Output instructions

package main
func main(){
  println("Hello, Go")
}

//console
Hello, Go

println is one of the "instructions" provided by Go.

Command "Print what's in println () to the console" → The computer outputs the character string to the console

Program structure

package main
func main(){
  println("Hello, Go")
}

The Go code file is composed of the package definition part and the function definition part.

Here, if you write the instruction in the {} of the main function of the file written as "package main" It is executed in order

Use numbers

package main
func main(){
  println(1)
  println(1 + 1)
  println(1 - 2)
  println("1 - 2")
}

//console
1
2
-1
1 - 2

Numbers are not enclosed in double quotes, unlike strings

Perform the calculation

package main
func main(){
  println(2 * 5) //multiplication
  println(6 / 2) //division
  println(9 % 2) //Put out the remainder
}

//console
10
3
1

Symbols used for such operations are called "operators" The type of operator depends on the programming language

String concatenation

package main
func main(){
  println("Hi" + "Go")
  println("1" + "2")
}

//console
Hi,Go
12

Use "+" on a string to make it a single string

What is a variable?

Box to store data (value) The box (variable) has a name (variable name), and you can retrieve the value from the variable by using the name.

Variables and data types

var number int 
//number(Variable name)、int(Data type)

var number string　
//number(Variable name)、string(Data type)

To use a variable, first define the variable "Var variable name data type"

Instruct the computer to create a variable

Data type

"Hello, Go" //String(string type)
3 //integer(int type)

Strings and numbers are called "data types"

Use variables

package main
func main(){
  var n int //Definition of variable n
  n = 100 //Put 100 in the variable n(substitute)order
  println(n) //Output 100 using n
}

//console
100

"=" Is a symbol for putting a value in a box called a variable

Definition and assignment

package main
func main(){
  var n int = 100
  println(n) 
}

//console
100

If you write "var n int = 100", you can define and assign variables at the same time.

package main

func main() {
    var message string = "Hello,world" //Define and assign the variable message
    println(message)
}

Update the value of a variable

package main
func main(){
  var n int = 100
  println(n)
  n = 200
  println(n)
}

//console
100
200

Variables can be overwritten as many times as you like

Data type abbreviation

package main
func main(){
  var n = 100
  println(n)
}

//console
100

When variable definition and value assignment are performed at the same time, such as "var n int = 100" Data type specification can be omitted

Because it is judged from the assigned value that Go is an int type

Omission of variable definition

package main
func main(){
  n := 100
  println(n)
}

//console
100

Same meaning as "var n int = 100" Note that it is ": ="

Convenient way to write println

package main
func main(){
  a := 100
  b := 200
  println(a,b)
}

//console
100 200

If you write variables a and b side by side in () of println separated by commas Two values can be output at the same time

Commas are not output, separated by spaces and displayed on one line

Go language-Basic ❷ is here

Go Language-Basic ❶