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Conditional and Loops in Go

Conditional Statements (if, else if, else)

num := 10
num_mod_3 := num % 3

if num_mod_3 == 0 {
    fmt.Println("Divisible by 3")
} else if num_mod_3 == 1 {
    fmt.Println("Remainder 1 when divided by 3")
} else {
    fmt.Println("Remainder 2 when divided by 3")
}

else if and else should immediately follow preceeding }

below code will not compile. Go’s syntax enforces clean code structure. 

if num_mod_3 == 0 {
    fmt.Println("Divisible by 3")
}
else if num_mod_3 == 1 {
    fmt.Println("Remainder 1 when divided by 3")
}
else {
    fmt.Println("Remainder 2 when divided by 3")
}

Switch Statement

  • Go only runs the selected case, not all the cases that follow.
  • In effect, the break statement that is needed at the end of each case in those languages is provided automatically in Go.
  • Another important difference is that Go's switch cases need not be constants, and the values involved need not be integers.
package main

import (
    "fmt"
    "runtime"
)

func main() {
    fmt.Print("Go runs on ")
    switch os := runtime.GOOS; os {
    case "darwin":
        fmt.Println("OS X.")
    case "linux":
        fmt.Println("Linux.")
    default:
        // freebsd, openbsd,
        // plan9, windows...
        fmt.Printf("%s.\n", os)
    }
}

Loops

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

for loop with range

  • range form of the for loop iterates over a slice or map
var pow = []int{1, 2, 4, 8, 16, 32, 64, 128}

for i, v := range pow {
    fmt.Printf("2**%d = %d\n", i, v)
}

performance penalty

  • range on a slice passes the copy of the value (not a reference) by default, this affects performance for large slices or complex data types
  • In cases where performance is critical, you might consider using an index-based loop to avoid the copy.

for loop with break

for i := 0; i < 10; i++ {
    if i == 5 {
        break
    }
    fmt.Println(i)
}

for loop with continue

for i := 0; i < 10; i++ {
    if i == 5 {
        continue
    }
    fmt.Println(i)
}

Infinite Loop

for {
    fmt.Println("Infinite loop")
}