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add: struct exercises and quiz

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This commit is contained in:
Inanc Gumus
2019-05-08 14:02:32 +03:00
parent dcf3b26791
commit 122947d990
13 changed files with 516 additions and 57 deletions
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2
24-structs/05-project-log-parser-structs/main.go
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@ -64,7 +64,7 @@ func main() {
p.total += visits p.total += visits
// You cannot assign to composite values // You cannot assign to composite values
// p.sum[name].count += visits // p.sum[domain].visits += visits
// create and assign a new copy of `visit` // create and assign a new copy of `visit`
p.sum[domain] = result{ p.sum[domain] = result{

19
24-structs/TODO.md
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@ -1,19 +0,0 @@
[x] what?
[x] why?
[x] struct type
[x] struct literal
[x] anonymous structs
[x] named structs
[x] struct fields
[x] compare and assign
[x] printing
[x] embedding
[ ] exporting struct and fields
[ ] struct tags {json encode/decode} - project?
**LATER:**
[ ] funcs: constructor pattern
[ ] pointers:
[ ] structs and pointers - later
[ ] padding and memory layout - later
[ ] using anonymous structs when testing

21
24-structs/exercises/00-name/main.go
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@ -1,21 +0,0 @@
// For more tutorials: https://blog.learngoprogramming.com
//
// Copyright © 2018 Inanc Gumus
// Learn Go Programming Course
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
//
package main
// ---------------------------------------------------------
// EXERCISE: ??
//
//
// EXPECTED OUTPUT
//
//
// ---------------------------------------------------------
func main() {
}

12
24-structs/exercises/00-name/solution/main.go
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@ -1,12 +0,0 @@
// For more tutorials: https://blog.learngoprogramming.com
//
// Copyright © 2018 Inanc Gumus
// Learn Go Programming Course
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
//
package main
func main() {
}

39
24-structs/exercises/01-warmup/main.go Normal file
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@ -0,0 +1,39 @@
// For more tutorials: https://blog.learngoprogramming.com
//
// Copyright © 2018 Inanc Gumus
// Learn Go Programming Course
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
//
package main
// ---------------------------------------------------------
// EXERCISE: Warm Up
//
// Starting with this exercise, you'll build a command-line
// game store.
//
// 1. Declare the following structs:
//
// + item: id (int), name (string), price (int)
//
// + game: embed the item, genre (string)
//
//
// 2. Create a game slice using the following data:
//
// id name price genre
//
// 1 god of war 50 action adventure
// 2 x-com 2 30 strategy
// 3 minecraft 20 sandbox
//
//
// 3. Print all the games.
//
// EXPECTED OUTPUT
// Please run the solution to see the output.
// ---------------------------------------------------------
func main() {
}

39
24-structs/exercises/01-warmup/solution/main.go Normal file
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@ -0,0 +1,39 @@
// For more tutorials: https://blog.learngoprogramming.com
//
// Copyright © 2018 Inanc Gumus
// Learn Go Programming Course
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
//
package main
import "fmt"
func main() {
type item struct {
id int
name string
price int
}
type game struct {
item
genre string
}
games := []game{
{
item: item{id: 1, name: "god of war", price: 50},
genre: "action adventure",
},
{item: item{id: 2, name: "x-com 2", price: 40}, genre: "strategy"},
{item: item{id: 3, name: "minecraft", price: 20}, genre: "sandbox"},
}
fmt.Printf("Inanc's game store has %d games.\n\n", len(games))
for _, g := range games {
fmt.Printf("#%d: %-15q %-20s $%d\n",
g.id, g.name, "("+g.genre+")", g.price)
}
}

33
24-structs/exercises/02-list/main.go Normal file
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@ -0,0 +1,33 @@
// For more tutorials: https://blog.learngoprogramming.com
//
// Copyright © 2018 Inanc Gumus
// Learn Go Programming Course
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
//
package main
// ---------------------------------------------------------
// EXERCISE: List
//
// Now, it's time to add an interface to your program using
// the bufio.Scanner. So the users can list the games, or
// search for the games by id.
//
// 1. Scan for the input in a loop (use bufio.Scanner)
//
// 2. Print the available commands.
//
// 3. Implement the quit command: Quits from the loop.
//
// 4. Implement the list command: Lists all the games.
//
//
// EXPECTED OUTPUT
// Please run the solution and try the program with list and
// quit commands.
// ---------------------------------------------------------
func main() {
// use your solution from the previous exercise
}

65
24-structs/exercises/02-list/solution/main.go Normal file
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@ -0,0 +1,65 @@
// For more tutorials: https://blog.learngoprogramming.com
//
// Copyright © 2018 Inanc Gumus
// Learn Go Programming Course
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
//
package main
import (
"bufio"
"fmt"
"os"
)
func main() {
type item struct {
id int
name string
price int
}
type game struct {
item
genre string
}
games := []game{
{
item: item{id: 1, name: "god of war", price: 50},
genre: "action adventure",
},
{item: item{id: 2, name: "x-com 2", price: 40}, genre: "strategy"},
{item: item{id: 3, name: "minecraft", price: 20}, genre: "sandbox"},
}
fmt.Printf("Inanc's game store has %d games.\n", len(games))
in := bufio.NewScanner(os.Stdin)
for {
fmt.Printf(`
> list : lists all the games
> quit : quits
`)
if !in.Scan() {
break
}
fmt.Println()
switch in.Text() {
case "quit":
fmt.Println("bye!")
return
case "list":
for _, g := range games {
fmt.Printf("#%d: %-15q %-20s $%d\n",
g.id, g.name, "("+g.genre+")", g.price)
}
}
}
}

47
24-structs/exercises/03-query-by-id/main.go Normal file
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@ -0,0 +1,47 @@
// For more tutorials: https://blog.learngoprogramming.com
//
// Copyright © 2018 Inanc Gumus
// Learn Go Programming Course
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
//
package main
// ---------------------------------------------------------
// EXERCISE: Query By Id
//
// Add a new command: "id". So the users can query the games
// by id.
//
// 1. Before the loop, index the games by id (use a map).
//
// 2. Add the "id" command.
// When a user types: id 2
// It should print only the game with id: 2.
//
// 3. Handle the errors:
//
// id
// wrong id
//
// id HEY
// wrong id
//
// id 10
// sorry. i don't have the game
//
// id 1
// #1: "god of war" (action adventure) $50
//
// id 2
// #2: "x-com 2" (strategy) $40
//
//
// EXPECTED OUTPUT
// Please also run the solution and try the program with
// list, quit, and id commands to see it in action.
// ---------------------------------------------------------
func main() {
// use your solution from the previous exercise
}

100
24-structs/exercises/03-query-by-id/solution/main.go Normal file
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@ -0,0 +1,100 @@
// For more tutorials: https://blog.learngoprogramming.com
//
// Copyright © 2018 Inanc Gumus
// Learn Go Programming Course
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
//
package main
import (
"bufio"
"fmt"
"os"
"strconv"
"strings"
)
func main() {
type item struct {
id int
name string
price int
}
type game struct {
item
genre string
}
games := []game{
{
item: item{id: 1, name: "god of war", price: 50},
genre: "action adventure",
},
{item: item{id: 2, name: "x-com 2", price: 40}, genre: "strategy"},
{item: item{id: 3, name: "minecraft", price: 20}, genre: "sandbox"},
}
// index the games by id
byID := make(map[int]game)
for _, g := range games {
byID[g.id] = g
}
fmt.Printf("Inanc's game store has %d games.\n", len(games))
in := bufio.NewScanner(os.Stdin)
for {
fmt.Printf(`
> list : lists all the games
> id N : queries a game by id
> quit : quits
`)
if !in.Scan() {
break
}
fmt.Println()
cmd := strings.Fields(in.Text())
if len(cmd) == 0 {
continue
}
switch cmd[0] {
case "quit":
fmt.Println("bye!")
return
case "list":
for _, g := range games {
fmt.Printf("#%d: %-15q %-20s $%d\n",
g.id, g.name, "("+g.genre+")", g.price)
}
case "id":
if len(cmd) != 2 {
fmt.Println("wrong id")
continue
}
id, err := strconv.Atoi(cmd[1])
if err != nil {
fmt.Println("wrong id")
continue
}
g, ok := byID[id]
if !ok {
fmt.Println("sorry. i don't have the game")
continue
}
fmt.Printf("#%d: %-15q %-20s $%d\n",
g.id, g.name, "("+g.genre+")", g.price)
}
}
}

16
24-structs/exercises/README.md
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@ -1,5 +1,15 @@
# Structs Exercises # Struct Exercises
## Warm-Up You'll build a queryable command-line game store.
1. **[?](https://github.com/inancgumus/learngo/tree/master/???)** 1. **[Warm Up](https://github.com/inancgumus/learngo/tree/master/24-structs/exercises/01-warmup)**
Load up the data into the game store.
2. **[List](https://github.com/inancgumus/learngo/tree/master/24-structs/exercises/02-list)**
Now, it's time to add an interface to your program using the bufio.Scanner. So the users can list the games, or search for the games by id.
3. **[Query By Id](https://github.com/inancgumus/learngo/tree/master/24-structs/exercises/03-query-by-id)**
Add a new command: "id". So the users can query the games by id.

178
24-structs/questions/README.md Normal file
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@ -0,0 +1,178 @@
## When should you use a struct type?
1. For storing the same type of values
2. For adding an additional type of values in runtime
3. For combining different types in a single type to represent a concept *CORRECT*
> **1:** Arrays, slices, and maps are better candidates for that.
>
> **2:** Struct fields are fixed at compile-time, you cannot add additional fields in runtime, neither you can remove them.
>
> **3:** That's right. A struct type combines different types of fields in a single type. You can use a struct type to represent a concept.
>
## What are the properties of struct fields?
1. They all should be of the same type
2. Each one should have a name and possibly a different type *CORRECT*
3. You can add additional fields in runtime
4. You can remove the existing fields in runtime
> **2:** Yes, each field should have a unique name. Also, each field should have a type, but every field can have a different type.
>
## What is wrong with the following code?
```go
type weather struct {
temperature, humidity float64
windSpeed float64
temperature float64
}
```
1. Nothing is wrong with it
2. `temperature, humidity float64` field is a syntax error
3. `temperature` field is not unique *CORRECT*
> **2:** That's a parallel definition. It defines two float64 fields: temperature and humidity. It is correct.
>
> **3:** Right! Struct field names should be unique.
>
## What is the zero-value of the following struct value?
```go
var movie struct {
title, genre string
rating float64
released bool
}
```
1. `{}`
2. `{title: "", genre: "", rating: 0, released: false}` *CORRECT*
3. `{title: "", genre: "", rating: 0, released: true}`
4. `{"title, genre": "", rating: 0, released: false}`
> **1:** That's an empty struct value with no fields.
>
> **2:** Right! Go initializes a struct's fields to zero-values depending on their type.
>
## What is the type of the following struct?
```go
avengers := struct {
title, genre string
rating float64
released bool
}{
"avengers: end game", "sci-fi", 8.9, true,
}
fmt.Printf("%T\n", avengers)
```
1. `struct{}`
2. `struct{ string; string; float64; bool }`
3. `struct{ title string; genre string; rating float64; released bool }` *CORRECT*
4. `{title: "avengers: end game"; genre: "sci-fi"; rating: 8.9; released: true}`
> **1:** That's an empty struct type with no fields.
>
> **2:** Fields names is also a part of a struct's type.
>
> **3:** Right! Field names and types are part of a struct's type.
>
> **4:** Nope, that's a struct value.
>
## Are the following struct values equal?
```go
type movie struct {
title, genre string
rating float64
released bool
}
avengers := movie{"avengers: end game", "sci-fi", 8.9, true}
clone := movie{
title: "avengers: end game", genre: "sci-fi",
rating: 8.9, released: true,
}
```
1. There is a syntax error
2. Yes *CORRECT*
3. No
> **2:** When creating a struct value, it doesn't matter whether you use the field names or not. So, they are equal.
>
## Are the following struct values equal? If not, why?
```go
type movie struct {
title, genre string
rating float64
released bool
}
avengers := movie{
title: "avengers: end game", genre: "sci-fi",
rating: 8.9, released: true,
}
clone := movie{title: "avengers: end game", genre: "sci-fi"}
fmt.Println(avengers == clone)
```
1. Yes: They have the same set of fields
2. No : They are not comparable
3. No : Field values are different *CORRECT*
> **1:** That's right, this means they are comparable, but that's not enough.
>
> **2:** Yes, they are. They use the same struct type.
>
> **3:** Yes, when you omit some of the fields, Go assigns zero values to them. Here, "clone" struct value's "rating" and "released" fields are: 0, and false, respectively.
>
## Do the movie and performance struct types have the same types?
```go
type item struct { title string }
type movie struct { item }
type performance struct { item }
```
1. Yes: They have the same set of fields
2. No : They have different type names *CORRECT*
3. No : An embedded field cannot be compared
> **2:** Right! Types with different names cannot be compared. However, you can convert one of them to the other because they have the same set of fields. movie{} == movie(performance{}) is ok, or vice versa.
>
## What does the program print?
```go
type item struct{ title string }
type movie struct {
item
title string
}
m := movie{
title: "avengers: end game",
item: item{"midnight in paris"},
}
fmt.Println(m.title, "&", m.item.title)
```
1. midnight in paris & midnight in paris
2. avengers: end game & avengers: end game
3. midnight in paris & avengers: end game
4. avengers: end game & midnight in paris *CORRECT*
> **4:** Right! `m.title` returns "avengers: end game" because the outer type always takes priority. However, `m.item.title` returns "midnight in paris" because you explicitly get it from the inner type: item.
>

2
30-concurrency/xxx-concurrent-downloader/fetch/session.go
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@ -32,8 +32,8 @@ func (s *Session) Start(transfers ...Transfer) <-chan Progress {
for _, t := range transfers { for _, t := range transfers {
go func(t Transfer) { go func(t Transfer) {
defer wg.Done()
t.Start(updates, s.done) t.Start(updates, s.done)
wg.Done()
}(t) }(t)
} }