If/Else · Tuck

Branching with if and else is straightforward. Parentheses around the condition are not needed, but braces are.

package main

import (
	"fmt"
	"strconv"
)

func main() {

A basic example.

	if 7%2 == 0 {
		fmt.Println("7 is even")
	} else {
		fmt.Println("7 is odd")
	}

An if without an else.

	if 8%4 == 0 {
		fmt.Println("8 is divisible by 4")
	}

Logical operators combine conditions.

	if 8%2 == 0 || 7%2 == 0 {
		fmt.Println("either 8 or 7 is even")
	}

A statement can come before the condition. Variables declared there are available in the current and all later branches.

	if num := 9; num < 0 {
		fmt.Println(num, "is negative")
	} else if num < 10 {
		fmt.Println(num, "has 1 digit")
	} else {
		fmt.Println(num, "has multiple digits")
	}

This is the most common shape in Go: call something, then check its error.

	if n, err := strconv.Atoi("42x"); err != nil {
		fmt.Println("error:", err)
	} else {
		fmt.Println("parsed", n)
	}

There is no ternary operator (a ? b : c) in Go; use a full if instead. Conditions must be booleans, there is no truthiness:

	// if 1 {}
	// error: non-boolean condition in if statement
}

$ go run ./06_if_else
7 is odd
8 is divisible by 4
either 8 or 7 is even
9 has 1 digit
error: strconv.Atoi: parsing "42x": invalid syntax

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