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fix: bouncing ball exercises

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This commit is contained in:
Inanc Gumus
2019-03-22 13:57:20 +03:00
parent 10e0ea269f
commit b0efd28975
8 changed files with 292 additions and 43 deletions
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119
18-project-bouncing-ball/exercises/01-find-the-bug/main.go Normal file
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@@ -0,0 +1,119 @@
// 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"
"time"
"github.com/inancgumus/screen"
)
// ---------------------------------------------------------
// EXERCISE: Find the Bug
//
// As I've annotated in the lectures, there is a bug
// in this code. Please find the bug and fix it.
//
//
// HINT #1
//
// 💀 Read this only if you get stuck.
//
// Print the width*height and the capacity of the drawing buffer
// after a single drawing loop ends. You might be surprised.
//
//
// HINT #2
//
// 💀 Read this only if you get stuck.
//
// The bug is in the drawing buffer. It doesn't include the
// newline and space characters when creating the buffer. So
// the buffer is not large enough to hold all the characters.
// So new backing arrays are getting allocated.
//
// ---------------------------------------------------------
func main() {
const (
width = 50
height = 10
cellEmpty = ' '
cellBall = '⚾'
maxFrames = 1200
speed = time.Second / 20
)
var (
px, py int // ball position
vx, vy = 1, 1 // velocities
cell rune // current cell (for caching)
)
// create the board
board := make([][]bool, width)
for column := range board {
board[column] = make([]bool, height)
}
// create a drawing buffer
buf := make([]rune, 0, width*height)
// clear the screen once
screen.Clear()
for i := 0; i < maxFrames; i++ {
// calculate the next ball position
px += vx
py += vy
// when the ball hits a border reverse its direction
if px <= 0 || px >= width-1 {
vx *= -1
}
if py <= 0 || py >= height-1 {
vy *= -1
}
// remove the previous ball
for y := range board[0] {
for x := range board {
board[x][y] = false
}
}
// put the new ball
board[px][py] = true
// rewind the buffer (allow appending from the beginning)
buf = buf[:0]
// draw the board into the buffer
for y := range board[0] {
for x := range board {
cell = cellEmpty
if board[x][y] {
cell = cellBall
}
buf = append(buf, cell, ' ')
}
buf = append(buf, '\n')
}
// print the buffer
screen.MoveTopLeft()
fmt.Print(string(buf))
// slow down the animation
time.Sleep(speed)
}
}

99
18-project-bouncing-ball/exercises/01-find-the-bug/solution/main.go Normal file
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@@ -0,0 +1,99 @@
// 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"
"time"
"github.com/inancgumus/screen"
)
func main() {
const (
width = 50
height = 10
cellEmpty = ' '
cellBall = '⚾'
maxFrames = 1200
speed = time.Second / 20
// drawing buffer length
// *2 for extra spaces
// +1 for newlines
bufLen = (width*2 + 1) * height
)
var (
px, py int // ball position
vx, vy = 1, 1 // velocities
cell rune // current cell (for caching)
)
// create the board
board := make([][]bool, width)
for column := range board {
board[column] = make([]bool, height)
}
// create a drawing buffer
// BUG FIXED!
buf := make([]rune, 0, bufLen)
// clear the screen once
screen.Clear()
for i := 0; i < maxFrames; i++ {
// calculate the next ball position
px += vx
py += vy
// when the ball hits a border reverse its direction
if px <= 0 || px >= width-1 {
vx *= -1
}
if py <= 0 || py >= height-1 {
vy *= -1
}
// remove the previous ball
for y := range board[0] {
for x := range board {
board[x][y] = false
}
}
// put the new ball
board[px][py] = true
// rewind the buffer (allow appending from the beginning)
buf = buf[:0]
// draw the board into the buffer
for y := range board[0] {
for x := range board {
cell = cellEmpty
if board[x][y] {
cell = cellBall
}
buf = append(buf, cell, ' ')
}
buf = append(buf, '\n')
}
// print the buffer
screen.MoveTopLeft()
fmt.Print(string(buf))
// slow down the animation
time.Sleep(speed)
}
}

26
18-project-bouncing-ball/exercises/01-width-and-height/main.go → 18-project-bouncing-ball/exercises/02-width-and-height/main.go
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@@ -5,6 +5,15 @@
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
//
package main
import (
"fmt"
"time"
"github.com/inancgumus/screen"
)
// ---------------------------------------------------------
// EXERCISE: Adjust the width and height automatically
//
@@ -88,15 +97,6 @@
//
// ---------------------------------------------------------
package main
import (
"fmt"
"time"
"github.com/inancgumus/screen"
)
func main() {
const (
width = 50
@@ -107,6 +107,12 @@ func main() {
maxFrames = 1200
speed = time.Second / 20
// drawing buffer length
//
// *2 for extra spaces
// +1 for newlines
bufLen = (width*2 + 1) * height
)
var (
@@ -123,7 +129,7 @@ func main() {
}
// create a drawing buffer
buf := make([]rune, 0, width*height)
buf := make([]rune, 0, bufLen)
// clear the screen once
screen.Clear()

7
18-project-bouncing-ball/exercises/01-width-and-height/solution/main.go → 18-project-bouncing-ball/exercises/02-width-and-height/solution/main.go
View File

@@ -57,8 +57,13 @@ func main() {
board[column] = make([]bool, height)
}
// drawing buffer length
// *2 for extra spaces
// +1 for newlines
bufLen := (width*2 + 1) * height
// create a drawing buffer
buf := make([]rune, 0, width*height)
buf := make([]rune, 0, bufLen)
// clear the screen once
screen.Clear()

7
18-project-bouncing-ball/exercises/02-previous-positions/main.go → 18-project-bouncing-ball/exercises/03-previous-positions/main.go
View File

@@ -72,8 +72,13 @@ func main() {
board[column] = make([]bool, height)
}
// drawing buffer length
// *2 for extra spaces
// +1 for newlines
bufLen := (width*2 + 1) * height
// create a drawing buffer
buf := make([]rune, 0, width*height)
buf := make([]rune, 0, bufLen)
// clear the screen once
screen.Clear()

16
18-project-bouncing-ball/exercises/02-previous-positions/solution/main.go → 18-project-bouncing-ball/exercises/03-previous-positions/solution/main.go
View File

@@ -23,13 +23,14 @@ func main() {
maxFrames = 1200
speed = time.Second / 20
initVx, initVy = 5, 2
// initial velocities
ivx, ivy = 5, 2
)
var (
px, py int // ball position
ppx, ppy int // previous ball position
vx, vy = initVx, initVy // velocities
vx, vy = ivx, ivx // velocities
cell rune // current cell (for caching)
)
@@ -50,8 +51,13 @@ func main() {
board[column] = make([]bool, height)
}
// drawing buffer length
// *2 for extra spaces
// +1 for newlines
bufLen := (width*2 + 1) * height
// create a drawing buffer
buf := make([]rune, 0, width*height)
buf := make([]rune, 0, bufLen)
// clear the screen once
screen.Clear()
@@ -62,10 +68,10 @@ func main() {
py += vy
// when the ball hits a border reverse its direction
if px <= 0 || px >= width-initVx {
if px <= 0 || px >= width-ivx {
vx *= -1
}
if py <= 0 || py >= height-initVy {
if py <= 0 || py >= height-ivx {
vy *= -1
}

16
18-project-bouncing-ball/exercises/03-single-dimensional/main.go → 18-project-bouncing-ball/exercises/04-single-dimensional/main.go
View File

@@ -43,13 +43,14 @@ func main() {
maxFrames = 1200
speed = time.Second / 20
initVx, initVy = 5, 2
// initial velocities
ivx, ivy = 5, 2
)
var (
px, py int // ball position
ppx, ppy int // previous ball position
vx, vy = initVx, initVy // velocities
vx, vy = ivx, ivy // velocities
cell rune // current cell (for caching)
)
@@ -70,8 +71,13 @@ func main() {
board[column] = make([]bool, height)
}
// drawing buffer length
// *2 for extra spaces
// +1 for newlines
bufLen := (width*2 + 1) * height
// create a drawing buffer
buf := make([]rune, 0, width*height)
buf := make([]rune, 0, bufLen)
// clear the screen once
screen.Clear()
@@ -82,10 +88,10 @@ func main() {
py += vy
// when the ball hits a border reverse its direction
if px <= 0 || px >= width-initVx {
if px <= 0 || px >= width-ivx {
vx *= -1
}
if py <= 0 || py >= height-initVy {
if py <= 0 || py >= height-ivy {
vy *= -1
}

19
18-project-bouncing-ball/exercises/03-single-dimensional/solution/main.go → 18-project-bouncing-ball/exercises/04-single-dimensional/solution/main.go
View File

@@ -23,13 +23,14 @@ func main() {
maxFrames = 1200
speed = time.Second / 20
initVx, initVy = 5, 2
// initial velocities
ivx, ivy = 5, 2
)
var (
px, py int // ball position
ppx, ppy int // previous ball position
vx, vy = initVx, initVy // velocities
vx, vy = ivx, ivy // velocities
cell rune // current cell (for caching)
)
@@ -47,8 +48,13 @@ func main() {
// create a single-dimensional board
board := make([]bool, width*height)
// drawing buffer length
// *2 for extra spaces
// +1 for newlines
bufLen := (width*2 + 1) * height
// create a drawing buffer
buf := make([]rune, 0, width*height)
buf := make([]rune, 0, bufLen)
// clear the screen once
screen.Clear()
@@ -59,15 +65,13 @@ func main() {
py += vy
// when the ball hits a border reverse its direction
if px <= 0 || px >= width-initVx {
if px <= 0 || px >= width-ivx {
vx *= -1
}
if py <= 0 || py >= height-initVy {
if py <= 0 || py >= height-ivy {
vy *= -1
}
// check whether the ball goes beyond the borders
if px < width && py < height {
// calculate the new and the previous ball positions
pos := py*width + px
ppos := ppy*width + ppx
@@ -77,7 +81,6 @@ func main() {
// save the previous positions
ppx, ppy = px, py
}
// rewind the buffer (allow appending from the beginning)
buf = buf[:0]