CODEWITHSUNDEEP
govariable-assignmentdeclaration
fronthem
fronthem

Reputation: 4139

Difference between "variable declaration" and "short variable declaration" at local scope in Go

According to this question how-to-define-a-single-byte-variable-in-go-lang

At a local scope:

var c byte = 'A'

and

c := byte('A')

My questions are:

  1. Do they have the same mechanism?
  2. Which one is more easy to understand by a go compiler?

Upvotes: 2

Views: 1092

Answers (1)

peterSO
peterSO

Reputation: 166598

They are the same type (byte is an alias for uint8) and value. For example,

package main

import "fmt"

func main() {
    var c byte = 'A'
    d := byte('A')
    fmt.Printf("c: %[1]T %[1]v d: %[2]T %[2]v c==d: %v", c, d, c == d)
}

Output:

c: uint8 65 d: uint8 65 c==d: true

They are equally efficient; the runtime code is the same. They are both easy to understand by Go compilers.

The Go Programming Language Specification.

A short variable declaration uses the syntax:

ShortVarDecl = IdentifierList ":=" ExpressionList .

It is shorthand for a regular variable declaration with initializer expressions but no types: 

"var" IdentifierList = ExpressionList .

The "best" is a matter of style. Which reads better in a given context?

The Go Programming Language

Alan A. A. Donovan · Brian W.Kernighan

Because of their brevity and flexibility, short variable declarations are used to declare and initialize the majority of local variables. A var declaration tends to be reserved for local variables that need an explicit type that differs from that of the initializer expression, or for when the variable will be assigned a value later and its initial value is unimportant.

Upvotes: 3

Related Questions