Go from zero: zero is a real value

If you declare a name and do not assign it, Go stores the zero value of the type. For an int that is 0. For a string that is empty text. Zero is a real value. A blank order is not an error from the language. It is a $0.00 charge with no drink name, unless your program refuses to print it.

Nothing is an empty slot#

Go will not leave a name uninitialized. If you declare cents and do not assign it, the memory is the zero of int, which is 0. A string's zero is the empty string, a bool's zero is false, a pointer's zero is nil, and a struct's zero is a struct of zeros. Zero is a value you can print, pass, and compare. It becomes a bug only when your program decided that 0 means "missing" and then charged it anyway. The language will not make that decision for you.

1. namestring(empty)
2. centsint0

package main

import "fmt"

func main() {
    var name string
    var cents int
    fmt.Printf("%q $%d.%02d\n", name, cents/100, cents%100)
}

"" $0.00

Read the zero before you charge it#

var name string makes name and stores "". var cents int makes cents and stores 0. %q prints the name in quotes, so an empty drink is visible. The dollars print as $0.00. Without the quotes, the empty name would look like a missing column and you might still charge nothing, or charge the next line by mistake.

A bool's zero is false. A pointer's zero is nil. A struct's zero is a struct whose fields are themselves zero: an Item you did not fill has Name == "" and Cents == 0. That item is usable. Label would print $0.00 with a blank name. If an order with no name is a bug, check the field before you print the label. Do not wait for Go to complain. It will not.

Zero is allowed to be the answer#

A bill that has not been started should be 0 cents. A name that has not been set should be empty. The mistake is treating every 0 as a failure, or treating 0 as safe to charge. The next lesson meets a zero that is not safe to write into: a map you have not made.