Golang Basic 6 - Basic for loop

for loop

• Go has only one looping construct, the for loop.
• The basic for loop has three components separated by semicolons:
  1. the init statement: executed before the first iteration.
  2. the condition expression: evaluated before every iteration.
  3. the post statement: executed at the end of every iteration.
• The init statement will often be a short variable declaration, and the variables declared there are visible only in the scope of the for statement.
• The loop will stop iterating once the boolean condition evaluates to false.
• Note: Unlike other languages like C, Java, or JavaScript there are no parentheses surrounding the three components of the for statement and the braces { } are always required.

Basic usage 1

Statement

for boolVal{
    /*
        if boolVal is true, run this code block.
        will stop while boolVal is false.
    */
}

Sample

root@go:l6/ # cat l6s1.go
package main
import (
    "fmt"
)
func main(){
    var i int
    for i <= 3{
        fmt.Println(i)
        i
    }
}
root@go:l6/ # go run l6s1.go
1
2
3

Basic usage 2

Statement

for initial; boolVal; repeat{
    /*
        if boolVal is true, run this code block.
        will stop while boolVal is false.
    */
}

Sample

root@go:l6/ # cat l6s2.go
package main
import (
    "fmt"
)
func main(){
    var i int
    for i = 1; i <= 3; i   {
        fmt.Println(i)
    }
}
root@go:l6/ # go run l6s2.go
1
2
3

Break

• You can use break statement to break current loop.

Statement

for boolVal{
    /*
        if boolVal is true, run this code block.
        will stop while boolVal is false.
    */
    if flag {
        // if flag is true, break the for loop.
        break
    }
}

Sample

root@go:l6/ # cat l6s3.go
package main
import (
    "fmt"
)
func main(){
    var i int
    for i = 1; i <= 3; i  {
        fmt.Println(i)
        if i == 2{
            break
        }
    }
}
root@go:l6/ # go run l6s3.go
1
2

Continue

• You can use continue, to pass current loop, continue running next loop.

Statement

for boolVal{
    /*
        if boolVal is true, run this code block.
        will stop while boolVal is false.
    */
    if flag {
        // if flag is true, break the for loop.
        continue
    }
    /*
        if the flag is effact, you can not see the result of statements here.
    */
}

Sample

root@go:l6/ # cat l6s4.go
package main
import (
    "fmt"
)
func main(){
    var i int
    for i = 1; i <= 3; i  {
        if i == 2{
            continue
        }
        fmt.Println(i)
    }
}
root@go:l6/ # go run l6s4.go
1
3