Loops

The Only Loop You Need

Go has exactly one loop keyword: for. It does the work of for, while, and do-while from other languages.

Classic For Loop

The three-component form, similar to C or Java:

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

While-Style Loop

Drop the init and post statements. You get a while loop:

n := 1
for n < 100 {
    n *= 2
}

Infinite Loop

In the TNG episode "Cause and Effect," the Enterprise gets stuck in a time loop, repeating the same disaster over and over. At least they did not have to debug an off-by-one error.

Drop everything. Use break to exit:

for {
    line := readInput()
    if line == "quit" {
        break
    }
}

Continue

continue skips to the next iteration:

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

For Range

The range keyword iterates over slices, arrays, strings, maps, and channels. It gives you both the index and the value:

names := []string{"Alice", "Bob", "Charlie"}
for i, name := range names {
    fmt.Printf("%d: %s\n", i, name)
}

Use _ to discard the index when you do not need it:

for _, name := range names {
    fmt.Println(name)
}

Your Task

Write a function fizzBuzz that takes an integer n and prints the numbers from 1 to n (inclusive), one per line, with these substitutions:

• Print "FizzBuzz" if the number is divisible by both 3 and 5
• Print "Fizz" if the number is divisible by 3
• Print "Buzz" if the number is divisible by 5
• Print the number otherwise