CODEWITHSUNDEEP
go
Saqib Ali
Saqib Ali

Reputation: 12575

Is there a nil value I can use for bytes in Go?

I'm implementing a tree in Go. My TreeNode struct looks like this:

type TreeNode struct {
    payload byte
    parent *TreeNode
    children map[byte]*TreeNode
}

In my implementation, the root node of the tree is a special node that has no payload. Otherwise the payload is always a single lower-case letter from the English alphabet. So my tree initialization function looks like this:

func createEmptyTree(fileName string) *TreeNode{
    return &TreeNode{
        nil,           // Line #180
        nil,
        false,
        map[byte]*TreeNode{},
    }
}

When I compile it though, I get the following error: ./main.go:180:9: cannot use nil as type byte in field value

So it seems I cannot use nil for a byte variable. Is there something else I could use in this situation? I could easily use '0' or other non alphabetic character. But it seems hacky. What should I do?

Upvotes: 2

Views: 9819

Answers (3)

peterSO
peterSO

Reputation: 166569

For idiomatic Go, write your function as:

package main

import (
    "fmt"
)

type TreeNode struct {
    payload  byte
    parent   *TreeNode
    children map[byte]*TreeNode
}

func createEmptyTree(fileName string) *TreeNode {
    return &TreeNode{
        children: map[byte]*TreeNode{},
    }
}

func main() {
    tree := createEmptyTree("fiename")
    fmt.Println(tree)
}

Playground: https://play.golang.org/p/v6DJCnpN6Ys

Output:

&{0 <nil> map[]}

The payload value for an empty tree is integer zero (0), the zero-value for the integer type byte. Zero is not a single lower-case letter value from the English alphabet.

The Go Programming Language Specification

The zero value

When storage is allocated for a variable, either through a declaration or a call of new, or when a new value is created, either through a composite literal or a call of make, and no explicit initialization is provided, the variable or value is given a default value. Each element of such a variable or value is set to the zero value for its type: false for booleans, 0 for numeric types, "" for strings, and nil for pointers, functions, interfaces, slices, channels, and maps.

Upvotes: 4

VonC
VonC

Reputation: 1324218

byte is a numeric type, actually an alias for uint8.

That means it has default zero value of 0.

Upvotes: 16

Greg Nisbet
Greg Nisbet

Reputation: 6994

Every type in golang has a zero value. In the case of byte that is the null byte.

It's entirely possible to just use the null byte as a magical zero payload at the root.

Upvotes: 0

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