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Pranava S Balugari
Pranava S Balugari

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GoLang for loop variations

Go has only one looping construct, the for loop. It comes with 2 variations from a usability point of view. Understanding the differences will definitely help in implementing the right one at the right time :).

Table Of Contents

Pointer semantic form

In this one the loop happens on the original continents array.

// Using the Pointer semantic form of for: <- range

package main

import "fmt"

func main() {
 continents := [3]string{'Asia', 'Africa','Australia'}
 fmt.Printf("Before -> [%s] : ", continents[1])

 for i := range continents {
    continents[1] = 'Europe'

    if i == 1 {   
       fmt.Printf("After -> [%s] : ", continents[1])
    }

 }

}

Output:
Before -> [Africa] : After -> [Europe]


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Value semantic form

In this one the looping happens on the copy of the original array.

// Using the value semantic form of for: <- range

package main

import "fmt"

func main() {
 continents := [3]string{'Asia', 'Africa','Australia'}
 fmt.Printf("Before -> [%s] : ", continents[1])

 for i, c := range continents {
    continents[1] = 'Europe'

    if i == 1 {   
       fmt.Printf("After -> [%s] : ", c)
    }

 }

}

Output:
Before -> [Africa] : After -> [Africa]


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There is one more value semantic form of the for range but with pointer semantic access. DON'T DO THIS.


package main

import "fmt"

func main() {
 continents := [3]string{'Asia', 'Africa','Australia'}
 fmt.Printf("Before -> [%s] : ", continents[1])

 for i, c := range &continents {
    continents[1] = 'Europe'

    if i == 1 {   
       fmt.Printf("After -> [%s] : ", c)
    }

 }

}

Output:
Before -> [Africa] : After -> [Europe]


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