Looping

• Looping
• For Statement
  • Simple Loops
  • Exiting Early
  • Looping through collections

For Statement

Simple Loops

package main

import (
    "fmt"
)

func main() {
    // initializer := 0, condition, incrementor
    // i scoped to for loop
    for i := 0; i < 10; i++ {
        fmt.Println(i)
    }

    // j scoped to main function
    j := 0
    for ; j < 10; j++ {
        fmt.Println(j)
    }    

    // incrementor inside the loop
    for i := 0; i < 10;  {
        fmt.Println(i)
        i++
    }

    // effectively a while loop
    // the two colons (;) around the condition are optional
    k := 0
    for ;k < 10 ; {
        fmt.Println(k)
        k++
    }
}

package main

import (
    "fmt"
)

func main() {
    // multiple counters
    for i, j := 0, 0; i < 5; i, j = i+1, j+1 {
        fmt.Println(i, j)
    }
}

package main

import (
    "fmt"
)

func main() {
    //  nested loops
    for i := 0; i < 3; i++ {
        for j := 0; j < 3; j++ {
            fmt.Println(i * j)
        }
    }
}

Exiting Early

package main

import (
    "fmt"
)

func main() {

    k := 0
    for {
        fmt.Println(k)
        k++
        if k == 5 {
            // breaks out of closest loop
            break
        }
    }
}

package main

import (
    "fmt"
)

func main() {
    // breaking out of outer loop
Loop:
    for i := 1; i <= 3; i++ {
        for j := 1; j <= 3; j++ {
            fmt.Println(i * j)
            if i*j >= 3 {
                break Loop
            }
        }
    }
}

package main

import (
    "fmt"
)

func main() {

    for i := 0; i < 10; i++ {
        if i%2 == 0 {
            continue
        }
        fmt.Println(i)
    }
}

Looping through collections

• can be done for slices, arrays, maps. strings and channels
• assign _ to key or value when you don't plan on using it

  package main
  
  import (
      "fmt"
  )
  
  func main() {
      s := []int{1,2,3}
      for k, v := range s {
          fmt.Println(k, v)
      }
  }