Summary - Control flow

Combine if, for and switch to write a score calculator.

Control flow summary

Decisions: if / else if / else (the condition must be a bool and can take a short statement) and switch (comma cases, expressionless switch, rarely fallthrough). Loops: the single keyword for — counter, condition, infinite and range. Flow control: break, continue, labels.

for i := range 15 {
    switch {
    case i%15 == 0:
        fmt.Println("FizzBuzz")
    case i%3 == 0:
        fmt.Println("Fizz")
    }
}

Early return

Go code prefers "early return" over nested if-else: error or special cases are handled at the top and the function returns, keeping the main flow unindented.

func indirim(tutar float64, uye bool) float64 {
    if tutar <= 0 {
        return 0
    }
    if !uye {
        return tutar
    }
    return tutar * 0.9
}

Exercise FizzBuzz

For the numbers 1 to 15: print FizzBuzz if divisible by 15, Fizz if divisible by 3, Buzz if divisible by 5, otherwise the number itself. Print them all on one line separated by spaces (with fmt.Print, then fmt.Println() at the end).

Show example solution

package main

import "fmt"

func main() {
    for i := 1; i <= 15; i++ {
        switch {
        case i%15 == 0:
            fmt.Print("FizzBuzz ")
        case i%3 == 0:
            fmt.Print("Fizz ")
        case i%5 == 0:
            fmt.Print("Buzz ")
        default:
            fmt.Print(i, " ")
        }
    }
    fmt.Println()
}

Test yourself

In FizzBuzz, why must the <code>i%15 == 0</code> check come first?
- Multiples of 15 are also divisible by 3; if 3 comes first it prints "Fizz"
- It's faster
- Go requires it
- The order doesn't matter
Show answer

Multiples of 15 are also divisible by 3; if 3 comes first it prints "Fizz" — In an expressionless switch the first true case runs; the most specific condition is written at the top.

range over integers

for i := ____ 3 {
    fmt.Println(i)  // 0 1 2
}

Show answer

for i := range 3 {
    fmt.Println(i)  // 0 1 2
}

Group summary

if-else

Decision
switch

Multi-way decision
for

All loops
break / continue

Loop control

Next lesson: Array declaration

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