A Tour of Go - Basics: Packages, variables, and functions.

Question 1

Go programs are made up of …

Answer 1

packages

Question 2

Which package do Go programs start in?

Answer 2

main

Question 3

By convention, the package name is the …

Answer 3

last element of the import path

Question 4

Give an example of a package statement?

Answer 4

package main

Question 5

Give and example of an import statement?

Answer 5

import "fmt"

Question 6

Give and example of a factored import statement?

Answer 6

import (
    "fmt"
    "math/rand"
)

Factored import statements are considered good style.

Question 7

What is an exported name?

Answer 7

In Go, and exported name begins with a capital letter.

When importing a package you can only refer to the exported names.

Question 8

Give an example of a function that adds two integers?

Answer 8

func add(x, y int) int {
    return x + y
}

Question 9

Function can return multiple results

Give an example of a function that swaps two strings?

Answer 9

func swap(x, y string) (string, string) {
    return y, x
}

Question 10

What is a naked return?

Answer 10

Go’s return values can be named. If so, they are treated as variables defined at the top of the function.

A return statement with no arguments will return the names return values.

Question 11

Describe the var statement.

Answer 11

The var statement declares a list of variables, the type is last.

A var statement can be used at package or function level.

var i, j int
var s string

Question 12

What is an initaliser?

Answer 12

A var declaration can include initialisers, one per variable.

If an initialiser is present, the type can be omitted; the variable will take the type of the initialiser.

var i int = 1
var s = "hello"

Question 13

What is a short variable declaration?

Answer 13

In functions, the := short assignment statement can be used in place of a var declaration with implicit type.

i, j := 1, 2
s := "hello"

Question 14

What are Go’s basic types?

Answer 14

bool

string

int  int8  int16  int32  int64
uint uint8 uint16 uint32 uint64 uintptr

byte // alias for uint8

rune // alias for int32
     // represents a Unicode code point

float32 float64

complex64 complex128

Question 15

What is a zero value?

Answer 15

Variables declared without an explicit initial value are given their zero value.

The zero value is:

• 0 for numeric types,
• false for the boolean type, and
• ”” (the empty string) for strings.

Question 16

What is a type conversion?

Answer 16

The expression T(v) converts the value v to the type T.

var i int = 1
var f float64 = float(i)

Question 17

What is type inference?

Answer 17

When declaring a variable without specifying an explicit type (either by using the := syntax or var = expression syntax), the variable’s type is inferred from the value on the right hand side.

Question 18

What are constants?

Answer 18

Constants are declared like variables, but with the const keyword.

Constants can be character, string, boolean, or numeric values.

Constants cannot be declared using the := syntax.

Question 19

What’s special about numeric constants?

Answer 19

They are high precision values.

const Big = 1 &laquo_space;100